NetworkCastle

Abstract of CCNA study guide-30 - OSPF 4

2011-11-22T23:01:00.001-08:00

Troubleshooting OSPF

This section will have you verify sample OSPF configurations and configuration outputs in order to troubleshoot, maintain, and fix OSPF-related issues.

Problem 1:

If you see a configuration as shown here, you must know that there is no way a router will accept this input because the wildcard is incorrect:

Router(config)#router ospf 1

Router(config-router)#network 10.0.0.0 255.0.0.0 area 0

This would be correct statement:

Router(config)#router ospf 1

Router(config-router)#network 10.0.0.0 0.255.255.255 area 0

Problem 2:

look at a figure and determine which of the routers will become the designated router of the area.

All the router OSPF priorities are at the default.

Notice the RIDs of each router. The routers with the highest RIDs are routers A and B, since they have the highest IP addresses. RouterB should be the DR and RouterA should be the BDR. Okay, now here’s the thing: Since elections do not occur on point-to-point links by default, RouterB is the best answer.

Problem 3:

Let’s use another command to verify an OSPF configuration: the show ip ospf interface command. Look at the following output for routers A and B and see if you can determine why the two directly connected routers cannot establish an adjacency:

RouterA#sh ip ospf interface e0/0

Ethernet0/0 is up, line protocol is up

Internet Address 172.16.1.2/16, Area 0

Process ID 2, Router ID 172.126.1.1, Network Type BROADCAST, Cost: 10

Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID) 172.16.1.2, interface address 172.16.1.1

No backup designated router on this network

Timer intervals configured, Hello 5, Dead 20, Wait 20, Retransmit 5

RouterB#sh ip ospf interface e0/0

Ethernet0/0 is up, line protocol is up

Internet Address 172.16.1.1/16, Area 0

Process ID 2, Router ID 172.126.1.1, Network Type BROADCAST, Cost: 10

Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID) 172.16.1.1, interface address 172.16.1.2

No backup designated router on this network

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Everything in the two outputs looks pretty good, except that the Hello and Dead timers are not the same. RouterA has Hello and Dead timers of 5 and 20, and RouterB has Hello and Dead timers of 10 and 40, which are the default timers for OSPF.

Problem 4:

Take a look at the network shown in Figure 7.8 with four routers and two different routing protocols.

If all parameters are set to default and redistribution is not configured, which path do you think RouterA will use to reach RouterD? Since IGRP has an AD of 100 and OSPF has an AD of 110, RouterA will send packets to RouterD through RouterC.

Problem 5:

Study Figure 7.9 carefully. You are running OSPF on the routers and an ISDN link provides connectivity to the remote sales office.

What type of route should be configured on the Corporate router to connect to the sales office’s remote network while minimizing network overhead on the ISDN link as shown in Figure 7.9?

The only way we can do that is to create a static route on the Corporate router to connect to the remote network; anything else would be too bandwidth intensive.

Configuring EIGRP and OSPF Summary Routes

This section will provide you with the commands to summarize both EIGRP and OSPF.

Figure 7.10 shows six networks with four block sizes of 4 (WAN links) and two block sizes of 8 (LAN connections). The network address used is 192.168.10.64 and with a block size of 32, the mask would be 255.255.255.224. On the core router, for EIGRP we’ll place the summary route on Ethernet0, which will advertise our summary route out to the backbone network (10.10.10.0 network). This will stop all six of our networks from being advertised individually and instead advertise them as one route to the other routers in the internetwork. Here is the complete configuration of EIGRP on the core router:

Core#config t

Core(config)#router eigrp 10

Core(config-router)#network 192.168.10.0

Core(config-router)#network 10.0.0.0

Core(config-router)#no auto-summary

Core(config-router)#interface ethernet 0

Core(config-if)#ip summary-address eigrp 10 192.168.10.64 255.255.255.224

The above EIGRP configuration for autonomous system 10 advertises directly connected networks 192.168.10.0 and 10.0.0.0. Since EIGRP auto-summarizes at classful boundaries, you must use the no auto-summary command as well. The summary route we will advertise to the backbone network is placed on the interface connected to the backbone, not under the routing process. This summary route tells EIGRP to find all networks in the 192.168.10.64 network with a block size of 32 and advertise them as one route out interface E0. This means, basically, that any packet with a destination IP address of 192.168.10.64 through

192.168.10.95 will be forwarded via this summary route.

To summarize the contiguous network with OSPF we used with the EIGRP example we need to configure OSPF into multiple areas, as shown in Figure 7.11.

To summarize area 1 into the area 0 backbone, use the following command under the OSPF Process ID. Here is the complete OSPF configuration for the Core (backbone) router:

Core#config t

Core(config)#router ospf 1

Core(config-router)#network 192.168.10.64 0.0.0.3 area 1

Core(config-router)#network 192.168.10.68 0.0.0.3 area 1

Core(config-router)#network 10.10.10.0 0.0.0.255 area 0

Core(config-router)#area 1 range 192.168.10.64 255.255.255.224

The no auto-summary command is not needed since OSPF does not summarize at any boundary by default. The preceding OSPF configuration will summarize all the networks from area 1 to the backbone area as one entry of 192.168.10.64/27.

Abstract of CCNA study guide-29 - OSPF 3

2011-11-22T23:00:00.001-08:00

OSPF DR and BDR Elections

I need to expand the section on designated routers and backup designated routers.

To start with, I need to make sure you fully understand the terms neighbors and adjacencies again.

Neighbors

Two routers won’t become neighbors unless they agree on the following:

- Area ID

- Authentication OSPF allows for the configuration of a password for a specific area.

- Hello and Dead intervals OSPF exchanges Hello packets on each segment. OSPF requires these intervals to be exactly the same between two neighbors. You can see these timers with the show ip ospf interface command.

Adjacencies

Adjacent routers are routers that go beyond the simple Hello exchange and proceed into the database exchange process.

In order to minimize the amount of information exchanged, OSPF elects one router to be a designated router (DR) and one router to be a backup designated router (BDR) on each multi-access segment.

The BDR is elected as a backup router in case the DR goes down. The idea behind this is that routers have a central point of contact for information exchange.

DR and BDR Elections

only segments that are broadcast and non-broadcast multi-access networks(such as Ethernet and Frame Relay) will perform DR and BDR elections. Point-to-point links, like a serial WAN for example, will not have a DR election process.

On a broadcast or non-broadcast multi-access network, the router with the highest OSPF priority on a segment will become the DR for that segment.

This priority is shown with the show ip ospf interface command, which is set to 1 by default. If all routers have the default priority set, the router with the highest Router ID (RID) will win.

The RID is determined by the highest IP address on any interface at the moment of OSPF startup. This can be overridden with a loopback (logical) interface.

If you set a router’s interface to a priority value of zero, that router won’t participate in the DR or BDR election on that interface.

OSPF and Loopback Interfaces

Loopback interfaces are logical interfaces, which are virtual, software-only interfaces. Using loopback interfaces with your OSPF configuration ensures that an interface is always active for OSPF processes.

By default, OSPF uses the highest IP address on any active interface at the moment of OSPF startup.

this can be overridden by a logical interface. The highest IP address of any logical interface will always become a router’s RID.

Configuring Loopback Interfaces

First, let’s see what the RID is on the Corp router with the show ip ospf command:

Corp#sh ip ospf

Routing Process "ospf 132" with ID 10.1.5.1

[output cut]

We can see that the RID is 10.1.5.1, or the serial 0/2/0 interface of the router. So let’s configure

a loopback interface using a completely different IP addressing scheme:

Corp(config)#int loopback 0

*Mar 22 01:23:14.206: %LINEPROTO-5-UPDOWN: Line protocol on Interface

Loopback0, changed state to up

Corp(config-if)#ip address 172.16.10.1 255.255.255.255

The IP scheme really doesn’t matter here, but each router has to be in a separate subnet. By using the /32 mask, we can use any IP address we want as long as the addresses are never the same on any two routers.

Let’s check into that by taking a look at the Corp’s RID:

Corp#sh ip ospf

Routing Process "ospf 132" with ID 10.1.5.1

What happened?

You should reboot the router or delete OSPF and re-create the database on your router to see the changes.

Now let’s look and see what our RID is:

Corp#sh ip ospf

Routing Process "ospf 132" with ID 172.16.1.1

there is one other way about adding a new RID for the router under the router ospf process-id command instead?

Here’s an example of doing that on the 871W router:

871W#sh ip ospf

Routing Process "ospf 1" with ID 10.1.12.1

871W#config t

871W(config)#router ospf 1

871W(config-router)#router-id 172.16.10.5

Reload or use "clear ip ospf process" command, for this to take effect

871W(config-router)#do clear ip ospf process

Reset ALL OSPF processes? [no]: yes

871W(config-router)#do sh ip ospf

Routing Process "ospf 1" with ID 172.16.10.5

We changed the RID without reloading the router! But wait—remember, we didn’t set a loopback (logical interface) yet. So let’s try that now—let’s set a logical interface IP address, reload the router, and see if the loopback interface overrides the router-id command we just used:

871W(config-router)#int lo0

871W(config-if)#ip address 172.16.10.6 255.255.255.255

871W(config-if)#^Z

871W#reload

System configuration has been modified. Save? [yes/no]: y

Building configuration...

871W#sh ip ospf

Routing Process "ospf 1" with ID 172.16.10.5

Well, there’s our answer. A logical (loopback) interface will not override the router-id command, and we don’t have to reboot the router to make it take effect as the RID.

OSPF Interface Priorities

we can use priorities instead of logical addresses to force a certain router to become the DR or BDR in a network.

R2#config t

R2(config)#int f0/0

R2(config-if)#ip ospf priority ?

<0-255> Priority

R2(config-if)#ip ospf priority 2

All router interfaces default to a priority of 1, so by setting this interface to 2, I’ve ensured that it will automatically become the DR of the LAN segment. Setting an interface to 255 means that no one can beat your router!

Notice that: Even if you change the priority of the interface, the router will not become the DR of the LAN segment until both the existing DR and the BDR are shut down.

You can see your priority with the show ip ospf interface command:

R2(config-if)#do show ip ospf int f0/0

FastEthernet0/0 is up, line protocol is up

Internet Address 10.1.13.1/24, Area 0

Process ID 132, Router ID 172.16.30.1, Network Type BROADCAST,Cost:1

Transmit Delay is 1 sec, State UP, Priority 2

Notice that, we have three options to ensure that Router will be elected the DR for the LAN segment:

- Configure the priority value of the interface of the router to a higher value than any other interface on the Ethernet network.

- Configure a loopback interface on the Router with an IP address higher than any IP address on the other routers.

- Change the priority value of Other Routers interfaces to zero.

Abstract of CCNA study guide-28 - OSPF 2

2011-11-22T22:58:00.001-08:00

Configuring OSPF

These two elements are the basic elements of OSPF configuration:

- Enabling OSPF

- Configuring OSPF areas

Enabling OSPF

The easiest way to configure OSPF is to just use a single area. Doing this requires a minimum of two commands.

Lab_A(config)#router ospf ?

<1-65535>

A value in the range 1–65,535 identifies the OSPF Process ID. It’s a unique number on this router that groups a series of OSPF configuration commands under a specific running process. Different OSPF routers don’t have to use the same Process ID in order to communicate. It’s local value that essentially has little meaning, but it cannot start at 0; it has to start at 1.

Configuring OSPF Areas

After identifying the OSPF process, you need to identify:

- The interfaces that you want to activate OSPF communications on

- The area in which each resides.

- The networks you’re going to advertise to others.

- Wildcards that with used in the configuration.

Here’s an OSPF basic configuration example for you:

Lab_A#config t

Lab_A(config)#router ospf 1

Lab_A(config-router)#network 10.0.0.0 0.255.255.255 area ?

<0-4294967295> OSPF area ID as a decimal value

A.B.C.D OSPF area ID in IP address format

Lab_A(config-router)#network 10.0.0.0 0.255.255.255 area 0

The areas can be any number from 0 to 4.2 billion. Don’t get these numbers confused with the Process ID, which is from 1 to 65,535.

The arguments of the network command are the network number (10.0.0.0) and the wildcard mask (0.255.255.255). The combination of these two numbers identifies the interfaces that OSPF will operate on. OSPF will use this command to find any interface on the router configured in the 10.0.0.0 network, and it will place any interface it finds into area 0.

A quick review of wildcards: A 0 octet in the wildcard mask indicates that the corresponding octet in the network must match exactly. On the other hand, a 255 indicates that you don’t care what the corresponding octet is in the network number.

Wildcard Example

let’s take a quick peek at a harder OSPF network configuration to find out what our OSPF network statements would be if we were using subnets and wildcards.

You have a router with these four subnets connected to four different interfaces:

_ 192.168.10.64/28

_ 192.168.10.80/28

_ 192.168.10.96/28

_ 192.168.10.8/30

All interfaces need to be in area 0. Seems to me, the easiest configuration would be this:

Test#config t

Test(config)#router ospf 1

Test(config-router)#network 192.168.10.0 0.0.0.255 area 0

But it’s not likely to cover the CCNA objectives for you! So let’s create a separate network statement for each interface using the subnet numbers and wildcards.

Test#config t

Test(config)#router ospf 1

Test(config-router)#network 192.168.10.64 0.0.0.15 area 0

Test(config-router)#network 192.168.10.80 0.0.0.15 area 0

Test(config-router)#network 192.168.10.96 0.0.0.15 area 0

Test(config-router)#network 192.168.10.8 0.0.0.3 area 0

when configuring wildcards, they’re always one less than the block size. A /28 is a block size of 16, so we’d add network statement using the subnet number and then add a wildcard of 15 interesting octet. For the /30, which is a block size of 4, we’d use a wildcard of 3.

Let’s use Figure 7.5 as an example and configure that network with OSPF using wildcards

Lab_A#config t

Lab_A(config)#router ospf 1

Lab_A(config-router)#network 192.168.10.64 0.0.0.7 area 0

Lab_A(config-router)#network 10.255.255.80 0.0.0.3 area 0

Lab_B#config t

Lab_B(config)#router ospf 1

Lab_B(config-router)#network 192.168.10.48 0.0.0.7 area 0

Lab_B(config-router)#network 10.255.255.80 0.0.0.3 area 0

Lab_B(config-router)#network 10.255.255.8 0.0.0.3 area 0

Lab_C#config t

Lab_C(config)#router ospf 1

Lab_C(config-router)#network 192.168.10.16 0.0.0.7 area 0

Lab_C(config-router)#network 10.255.255.8 0.0.0.3 area 0

Verifying OSPF Configuration

There are several ways to verify proper OSPF configuration and operation:

First let’s issue a show ip route command on the Corp router:

10.0.0.0/24 is subnetted, 12 subnets

O 10.1.11.0 [110/65] via 10.1.5.2, 00:01:31, Serial0/2/0

O 10.1.10.0 [110/65] via 10.1.5.2, 00:01:31, Serial0/2/0

O 10.1.6.0 [110/74] via 10.1.3.2, 00:01:32, Serial0/0/1

[110/74] via 10.1.2.2, 00:01:32, Serial0/0/0

C 10.1.5.0 is directly connected, Serial0/2/0

C 10.1.4.0 is directly connected, Serial0/1/0

The Corp router shows the routes for our networks, with the O representing OSPF internal routes

Important note: OSPF can load-balance only across links of equal costs. It can’t load-balance across unequal-cost links as EIGRP can.

It’s time to show you all the OSPF verification commands that you need to know.

The show ip ospf Command

The show ip ospf command is used to display OSPF information for one or all OSPF processes running on the router. Information includes the Router ID, area information, SPF statistics, and LSA timer information:

Corp#sh ip ospf

Routing Process "ospf 132" with ID 10.1.5.1

Start time: 04:32:04.116, Time elapsed: 01:27:10.156

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

-------cut out --------------------

Notice the Router ID (RID) of 10.1.5.1, which is the highest IP address configured on the router.

The show ip ospf database Command

Using the show ip ospf database command will give you information about the number of routers in the internetwork (AS) plus the neighboring router’s ID (this is the topology database I mentioned earlier).

Unlike the show ip eigrp topology command, this command shows the “OSPF routers,” not each and every link in the AS as EIGRP does.

The output is broken down by area. Here’s a sample output, again from Corp:

Corp#sh ip ospf database

OSPF Router with ID (10.1.5.1) (Process ID 132)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

10.1.5.1 10.1.5.1 72 0x80000002 0x00F2CA 9

10.1.7.1 10.1.7.1 83 0x80000004 0x009197 6

10.1.9.1 10.1.9.1 73 0x80000001 0x00DA1C 4

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

10.1.11.2 10.1.12.1 68 0x80000001 0x00A337

The show ip ospf interface Command

The show ip ospf interface command displays all interface-related OSPF information.

Data is displayed about OSPF information for all interfaces or for specified interfaces. (I’ll bold some of the important things.)

Corp#sh ip ospf interface f0/1

FastEthernet0/1 is up, line protocol is up

Internet Address 10.1.1.1/24, Area 0

Process ID 132, Router ID 10.1.5.1, Network Type BROADCAST, Cost: 1

Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID) 10.1.5.1, Interface address 10.1.1.1

No backup designated router on this network

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

oob-resync timeout 40

Hello due in 00:00:01

Supports Link-local Signaling (LLS)

Index 1/1, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 0, maximum is 0

Last flood scan time is 0 msec, maximum is 0 msec

Neighbor Count is 0, Adjacent neighbor count is 0

Suppress hello for 0 neighbor(s)

The following information is displayed by this command:

- Interface IP address

- Area assignment

- Process ID

- Router ID

- Network type

-Cost

- Priority

- DR/BDR election information (if applicable)

- Hello and Dead timer intervals

- Adjacent neighbor information

The show ip ospf neighbor Command

The show ip ospf neighbor command is super-useful because it summarizes the pertinent OSPF information regarding neighbors and the adjacency state. If a DR or BDR exists, that information will also be displayed. Here’s a sample:

Corp#sh ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

10.1.11.1 0 FULL/ - 00:00:37 10.1.5.2 Serial0/2/0

10.1.9.1 0 FULL/ - 00:00:34 10.1.4.2 Serial0/1/0

10.1.7.1 0 FULL/ - 00:00:38 10.1.3.2 Serial0/0/1

10.1.7.1 0 FULL/ - 00:00:34 10.1.2.2 Serial0/0/0

Let’s take a look at the R3 and 871W routers outputs:

R3#sh ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

10.1.5.1 0 FULL/ - 00:00:39 10.1.5.1 Serial0/0/1

10.1.11.2 1 FULL/BDR 00:00:31 10.1.11.2 FastEthernet0/1

871W#sh ip ospf nei

Neihbor ID Pri State Dead Time Address Interface

10.1.11.1 1 FULL/DR 00:00:30 10.1.11.1 Vlan1

Since there’s an Ethernet link (broadcast multi-access) on the Corp router, there’s going to be an election to determine who will be the designated router and who will be the non-designated router. The 871W became the designated router because it had the highest IP address on the network.

The reason that the Corp connections to R1, R2, and R3 don’t have a DR or BDR listed in the output is that, elections don’t happen on point-to-point links.

The show ip protocols Command

The show ip protocols command provides an excellent overview of the actual operation of all currently running protocols. Check out the output from the Corp router:

Corp#sh ip protocols

Routing Protocol is "ospf 132"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 10.1.5.1

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Maximum path: 4

Routing for Networks:

10.1.1.1 0.0.0.0 area 0

10.1.2.1 0.0.0.0 area 0

10.1.3.1 0.0.0.0 area 0

10.1.4.1 0.0.0.0 area 0

10.1.5.1 0.0.0.0 area 0

Reference bandwidth unit is 100 mbps

Routing Information Sources:

Gateway Distance Last Update

10.1.11.1 110 00:28:53

10.1.11.2 110 00:28:53

10.1.9.1 110 00:28:53

10.1.7.1 110 00:28:53

Distance: (default is 110)

From looking at this output, you can determine the OSPF Process ID, OSPF Router ID, type of OSPF area, networks and areas configured for OSPF, and the OSPF Router IDs of neighbors.

Debugging OSPF

TABLE 7 . 4 Debugging Commands for Troubleshooting OSPF

Command	Description/Function
Debug ip ospf packet	Shows Hello packets being sent and received on your router
Debug ip ospf hello	Shows more detail than the debug ip ospf packet output
Debug ip ospf adj	Shows DR and DBR elections

Abstract of CCNA study guide-27 - OSPF 1

2011-11-22T22:55:00.001-08:00

Open Shortest Path First (OSPF) Basics

Open Shortest Path First (OSPF) is an open standard routing protocol that’s been implemented by a wide variety of network vendors, including Cisco. If you have multiple routers and not all of them are Cisco (what!), then you can’t use EIGRP, can you? So your remaining CCNA objective options are basically RIP, RIPv2, and OSPF. If it’s a large network, then, really, your only options are OSPF.

OSPF works by using the Dijkstra algorithm. First, a shortest path tree is constructed, and then the routing table is populated with the resulting best paths. OSPF converges quickly, although perhaps not as quickly as EIGRP, and it supports multiple, equal-cost routes to the same destination. Like EIGRP, it does support both IP and IPv6 routed protocols.

OSPF provides the following features:

- Consists of areas and autonomous systems

- Minimizes routing update traffic

- Allows scalability

- Supports VLSM/CIDR

- Has unlimited hop count

- Allows multi-vendor deployment (open standard)

OSPF is the first link-state routing protocol that most people are introduced to.

TABLE 7.3 OSPF and RIP Comparison

Characteristic	OSPF	RIPv2	RIPv1
Type of protocol	Link state	Distance vector	Distance vector
Classless support	Yes	Yes	No
VLSM support	Yes	Yes	No
Auto-summarization	No	Yes	Yes
Manual summarization	Yes	No	No
Discontiguous support	Yes	Yes	No
Route propagation	Multicast on change	Periodic multicast	Periodic broadcast
Path metric	Bandwidth	Hops	Hops
Hop count limit	None	15	15
Convergence	Fast	Slow	Slow
Peer authentication	Yes	Yes	No
Hierarchical network	Yes (using areas)	No (flat only)	No (flat only)
Updates	Event triggered	Route table updates	Route table updates
Route computation	Dijkstra	Bellman-Ford	Bellman-Ford

OSPF is designed in a hierarchical fashion, which basically means that you can separate the larger internetwork into smaller internetworks called areas. This is the best design for OSPF.

The following are reasons for creating OSPF in a hierarchical design:

- To decrease routing overhead

- To speed up convergence

- To confine network instability to single areas of the network

Figure 7.4 shows a typical OSPF simple design.

- Notice how each router connects to the backbone called area 0, or the backbone area. OSPF must have an area 0, and all other areas should connect to this area.

- Routers that connect other areas to the backbone area within an AS are called Area Border Routers (ABRs). Still, at least one interface of the ABR must be in area 0.

- OSPF runs inside an autonomous system, but it can also connect multiple autonomous systems together. The router that connects these ASes is called an Autonomous System Boundary Router (ASBR).

OSPF Terminology

Link A link is a network or router interface assigned to any given network.

Router ID (RID) is an IP address used to identify the router. the Router ID assigned using the highest IP address of all configured loopback interfaces. If no loopback interfaces are configured, OSPF will choose the highest IP address of all active physical interfaces.

Neighbor : Neighbors are two or more routers that have an interface on a common network, such as two routers connected on a point-to-point serial link.

Adjacency : is a relationship between two OSPF routers that permits the direct exchange of route updates.

Hello protocol : provides dynamic neighbor discovery and maintains neighbor relationships.

Neighborship database: is a list of all OSPF routers for which Hello packets have been seen.

Topological database :contains information from all of the Link State Advertisement packets that have been received for an area.

Link State Advertisement (LSA) is an OSPF data packet containing link-state and routing information that’s shared among OSPF routers.

Designated router (DR) is elected whenever OSPF routers are connected to the same multi-access network. Cisco likes to call these “broadcast” networks

Backup designated router (BDR) is standby for the DR on multi-access link. The BDR receives all routing updates from OSPF adjacent routers but doesn’t flood LSA updates.

OSPF areas is a grouping of contiguous networks and routers. All routers in the same area share a common Area ID

Broadcast (multi-access) such as Ethernet allow multiple devices to connect to (or access) the same network as well as provide a broadcast ability in which a single packet is delivered to all nodes on the network. In OSPF, a DR and a BDR must be elected for each broadcast multi-access network.

Non-broadcast multi-access: (NBMA) networks are types such as Frame Relay, X.25, and Asynchronous Transfer Mode (ATM). These networks allow for multi-access but have no broadcast ability like Ethernet. So, NBMA networks require special OSPF configuration to function properly and neighbor relationships must be defined.

Point-to-point : refers to a type of network topology consisting of a direct connection between two routers that provides a single communication path. This type of configuration eliminates the need for DRs or

BDRs—but neighbors are discovered automatically.

Point-to-multipoint : refers to a type of network topology consisting of a series of connections between a single interface on one router and multiple destination routers.

As with point-to-point, no DRs or BDRs are needed.

SPF Tree Calculation

Within an area, each router calculates the best/shortest path to every network in that same area. This calculation is based upon the information collected in the topology database and an algorithm called shortest path first (SPF).

each router in an area constructing a tree where the router is the root and all other networks are arranged

along the branches and leaves. This is the shortest path tree used by the router to insert routes into the routing table.

It’s important to understand that this tree contains only networks that exist in the same area as the router itself does. If a router has interfaces in multiple areas, then separate trees will be constructed for each area.

OSPF uses a metric referred to as cost. The cost of the entire path is the sum of the costs of the outgoing interfaces along the path.

Cisco uses a simple equation of 10^8 / bandwidth. The bandwidth is the configured bandwidth for the interface.

Using this rule, a 100Mbps Fast Ethernet interface would have a default OSPF cost of 1 and a 10Mbps Ethernet interface would have a cost of 10.An interface set with a bandwidth of 64,000 would have a default cost of 1,563.

This value may be overridden by using the ip ospf cost command. The cost is manipulated by changing the value to a number within the range of 1 to 65,535. Because the cost is assigned to each link, the value must be changed on the interface that you want to change the cost.

Abstract of CCNA study guide-26 - EIGRP 2

2011-11-22T22:52:00.001-08:00

Configuring EIGRP

To start an EIGRP session on a router, use the router eigrp command followed by the autonomous system number of your network.

Then use the network command followed by the network numbers connected to the router.

Example of enabling EIGRP for autonomous system 20 on a router connected to two networks, with the network numbers being 10.3.1.0/24 and 172.16.10.0/24:

Router#config t

Router(config)#router eigrp 20

Router(config-router)#network 172.16.0.0

Router(config-router)#network 10.0.0.0

Remember—as with RIP, you use the classful network address, which is all subnet and host bits turned off.

Understand that the AS number is the same in all routers , You can use any number from 1 to 65,535.

If you need to stop EIGRP from working on a specific interface, such as a BRI interface or a serial connection to the Internet. you would flag the interface as passive using the passive-interface interface command:

Router(config)#router eigrp 20

Router(config-router)#passive-interface serial 0/1

Doing this will prohibit the interface from sending or receiving Hello packets and, This means that it won’t send or receive route information on this interface.

Ex.

Corp#config t

Corp(config)#router eigrp ?

<1-65535> Autonomous system number

Corp(config)#router eigrp 10

Corp(config-router)#network 10.0.0.0

As with RIPv1,you still need to add the classful network numbers you want to advertise. But unlike RIP,

EIGRP uses classless routing—but you still configure it as classful. Classless, which I’m sure

you remember, means that the subnet mask information is sent along with routing protocol

updates (RIPv2 is classless).

Configuring Discontiguous Networks

Remember first Figure and how it demonstrated how EIGRP would auto-summarize the boundaries on a discontiguous network? Take a look at that figure again, Both routers, by default, would automatically summarize the classful boundaries and routing would not work. Here’s the configuration that would make this network work:

Lab_A#config t

Lab_A(config)#router eigrp 100

Lab_A(config-router)#network 172.16.0.0

Lab_A(config-router)#network 10.0.0.0

Lab_A(config-router)#no auto-summary

Lab_B#config t

Lab_B(config)#router eigrp 100

Lab_B(config-router)#network 172.16.0.0

Lab_B(config-router)#network 10.0.0.0

Lab_B(config-router)#no auto-summary

Because I used the no auto-summary command, EIGRP will advertise all the subnets between the two routers.

Load Balancing with EIGRP

By default, EIGRP can load-balance up to four equal-cost links. And we can configure EIGRP to load-balance across up to six equal-/unequal cost.

First, let’s take a look at the R1 routing table and make sure that EIGRP has already found both links between the routers:

R1#sh ip route

10.0.0.0/24 is subnetted, 12 subnets

D 10.1.11.0 [90/2684416] via 10.1.3.1, 00:50:37, Serial0/0/1

[90/2684416] via 10.1.2.1, 00:50:37, Serial0/0/0

D 10.1.9.0 [90/2707456] via 10.1.3.1, 01:24:09, Serial0/0/1

[90/2707456] via 10.1.2.1, 01:24:09, Serial0/0/0

D 10.1.8.0 [90/2707456] via 10.1.3.1, 01:24:09, Serial0/0/1

[90/2707456] via 10.1.2.1, 01:24:09, Serial0/0/0

D 10.1.12.0 [90/2684416] via 10.1.3.1, 00:10:10, Serial0/0/1

[90/2684416] via 10.1.2.1, 00:10:10, Serial0/0/0

C 10.1.3.0 is directly connected, Serial0/0/1

C 10.1.2.0 is directly connected, Serial0/0/0

You can see that we have two links to every route in our internetwork, and again, EIGRP will load balance across the s0/0/0 and s0/0/1 links by default because they’re the same metric.

EIGRP is automatic load balancing. But how about bundling links? Well, EIGRP can allow us to do this too—even with no extra configuration! Let me show you how this works. I’m going to configure the links between our Corp and R1 routers with the same subnet, meaning both links will have all interfaces within the same subnet. Check out my configuration:

Corp#config t

Corp(config)#int s0/0/1

Corp(config-if)#ip address 10.1.2.4 255.255.255.0

R1#config t

R1(config)#int s0/0/1

R1(config-if)#ip address 10.1.2.3 255.255.255.0

R1(config-if)#do show run | begin interface

interface Serial0/0/0

description 1st Connection to Corp Router

ip address 10.1.2.2 255.255.255.0

interface Serial0/0/1

description 2nd connection to Corp Router

ip address 10.1.2.3 255.255.255.0

Now both links have all four interfaces in the same subnet.

R1(config-if)#do show ip route

10.0.0.0/24 is subnetted, 12 subnets

D 10.1.11.0 [90/2684416] via 10.1.2.4, 00:04:44, Serial0/0/1

[90/2684416] via 10.1.2.1, 00:04:44, Serial0/0/0

D 10.1.10.0 [90/2707456] via 10.1.2.4, 00:04:44, Serial0/0/1

[90/2707456] via 10.1.2.1, 00:04:44, Serial0/0/0

D 10.1.9.0 [90/2707456] via 10.1.2.4, 00:04:44, Serial0/0/1

[90/2707456] via 10.1.2.1, 00:04:44, Serial0/0/0

D 10.1.8.0 [90/2707456] via 10.1.2.4, 00:04:44, Serial0/0/1

[90/2707456] via 10.1.2.1, 00:04:44, Serial0/0/0

D 10.1.12.0 [90/2684416] via 10.1.2.4, 00:04:44, Serial0/0/1

[90/2684416] via 10.1.2.1, 00:04:44, Serial0/0/0

C 10.1.2.0 is directly connected, Serial0/0/0

is directly connected, Serial0/0/1

D 10.1.1.0 [90/2172416] via 10.1.2.4, 00:03:56, Serial0/0/1

[90/2172416] via 10.1.2.1, 00:03:56, Serial0/0/0

C 10.1.7.0 is directly connected, FastEthernet0/1

There are two changes in the routing table now? Networks 10.1.2.0 and 10.1.3.0 used to show up as individual, directly connected interfaces, but not anymore. Now only the 10.1.2.0 network shows up as two directly connected interfaces, and the router now has a 3MB pipe through that line instead of just two 1.5Mbps T1 links.

Verifying EIGRP

There are several commands can be used to help you troubleshoot and verify the EIGRP configuration:

Next TABLE EIGRP Troubleshooting Commands

Command	Description/Function
show ip route	Shows the entire routing table
show ip route eigrp	Shows only EIGRP entries in the routing table
show ip eigrp neighbors	Shows all EIGRP neighbors
show ip eigrp topology	Shows entries in the EIGRP topology table
debug eigrp packet	Shows Hello packets sent/received between adjacent routers
Debug ip eigrp notification	Shows EIGRP changes and updates

The following router output is from the Corp router in our example:

Show ip eigrp neighbors command:

Corp#sh ip eigrp neighbors

IP-EIGRP neighbors for process 10

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

1 10.1.3.2 Se0/0/1 14 00:35:10 1 200 0 81

2 10.1.4.2 Se0/1/0 13 03:17:20 1 200 0 20

0 10.1.2.2 Se0/0/0 10 03:19:37 1 200 0 80

We read the information in this output like this:

- The H field: the order in which the neighbor was discovered.

- The hold time: how long this router will wait for a Hello packet to arrive from a specific neighbor.

- The uptime: how long the neighborship has been established.

- The SRTT field: the smooth round-trip timer—an indication of the time it takes for a round-trip from this router to its neighbor and back.

The time between multicast attempts is specified by…

- The Retransmission Time Out (RTO) field: the amount of time EIGRP waits before retransmitting a packet to a neighbor.

- The Q value: indicates whether there are any outstanding messages in the queue.

- The Seq field: indicates the sequence number of the last update from that neighbor.

The show ip eigrp neighbors command allows you to check the IP addresses ,the retransmit interval and queue counts for the neighbors that have established an adjacency.

show ip eigrp topology command :

Corp#sh ip eigrp topology

IP-EIGRP Topology Table for AS(10)/ID(10.1.5.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

r - reply Status, s - sia Status

P 10.1.11.0/24, 1 successors, FD is 2172416 via 10.1.5.2 (2172416/28160), Serial0/2/0

P 10.1.12.0/24, 1 successors, FD is 2172416 via 10.1.5.2 (2172416/28160), Serial0/2/0

P 10.1.3.0/24, 1 successors, FD is 76839936 via Connected, Serial0/0/1

via 10.1.2.2 (9849856/7719936), Serial0/0/0

P 10.1.2.0/24, 1 successors, FD is 2169856 via Connected, Serial0/0/0

via 10.1.2.2 (2681856/551936), Serial0/0/0

P 10.1.1.0/24, 1 successors, FD is 28160 via Connected, FastEthernet0/1

Notice that every route is preceded by a P. This means that the route is in the passive state, which is a good thing because routes in the active state (A) indicate that the router has lost its path to this network and is searching for a replacement.

Each entry indicates the feasible distance (FD), to each remote network plus the next-hop neighbor.

Plus, each entry also has two numbers in parentheses. The first indicates the feasible distance, and the second the advertised distance to a remote network.

Now here’s where things get interesting—notice that under the 10.1.7.0 and 10.1.6.0 outputs there are two links to each network and that the feasible distance and advertised distance are different. What this means is that we have one successor to the networks and one feasible successor (a backup route)remember that even though both routes to network 10.1.6.0 and 10.1.7.0 are in the topology table, only the successor route (the one

with the lowest metrics) will be copied and placed into the routing table.

EIGRP will load-balance across both links automatically when they are of equal variance (equal

cost), but EIGRP can also load-balance across unequal-cost links as well if we use the variance

command. The variance metric is set to 1 by default you can change the metric anywhere up to 128.

if the variance is set to 1, only routes with the same metric as the successor will be installed in the local routing table. And, if the variance is set to 2, any EIGRP learned route with a metric less than two times the successor metric will be installed in the local routing table (if it is already a feasible successor).

Debug eigrp packet command :that will show our Hello packets being sent between neighbor routers:

Corp#debug eigrp packet

EIGRP Packets debugging is on

(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB,

SIAQUERY, SIAREPLY)

Corp#

*Mar 21 23:17:35.050: EIGRP: Sending HELLO on FastEthernet0/1

*Mar 21 23:17:35.050: AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0

debug ip eigrp notification command :this command’s output shouldn’t show you anything at all! That’s right—the only time you’ll see output from this command is if there’s a problem on your network or you’ve added or deleted a network from a router

Abstract of CCNA study guide-25 - EIGRP 1

2011-11-22T22:50:00.001-08:00

EIGRP Features and Operation

Enhanced IGRP (EIGRP) is:

- Classless

- enhanced distance-vector protocol

- used in autonomous system

- includes the subnet mask in its route updates.

- Allow using (VLSMs) and summarization

- EIGRP is a hybrid routing protocol because it has characteristics of both distance-vector and link-state protocols.

§ As distance vector : it sends distance-vector updates about networks plus the cost of reaching them

§ As link state: synchronizes routing tables between neighbors at startup and then sends specific updates only when topology changes occur.

- EIGRP has a maximum hop count of 255 (default is 100).

There are a number of powerful features that make EIGRP a real standout from IGRP and other protocols:

- Support for IP and IPv6 via protocol dependent modules

- Considered classless (same as RIPv2 and OSPF)

- Support for VLSM/CIDR

- Support for summaries and discontiguous networks

- Efficient neighbor discovery

- Communication via Reliable Transport Protocol (RTP)

- Best path selection via Diffusing Update Algorithm (DUAL)

Protocol-Dependent Modules (PDM)

EIGRP provides routing support for multiple Network layer protocols: IP, IPX, AppleTalk, and now IPv6. That routing support comes through the use of protocol-dependent modules (PDMs).

Each EIGRP PDM will maintain a separate series of tables containing the routing information that applies to a specific protocol. What this means to you is that there will be IP/EIGRP tables and IPv6/EIGRP tables, for example.

Neighbor Discovery

There are three conditions that must be met for neighborship establishment (adjacencies):

- Hello or ACK received

- AS numbers match

- Identical metrics (K values)

Link-state protocols use Hello messages to establish neighborship (also called adjacencies)

The only time EIGRP advertises its entire routing table is when it discovers a new neighbor and forms an adjacency with it through the exchange of Hello packets. When this happens, both neighbors advertise their entire routing tables to one another. After each has learned its neighbor’s routes, only changes to the routing table are propagated from then on.

When EIGRP routers receive their neighbors’ updates, they store them in a local topology table. This table contains all known routes from all known neighbors and serves as the raw material from which the best routes are selected and placed into the routing table.

Let’s define some terms before we move on:

Feasible distance: This is the best metric along all paths to a remote network, including the metric to the neighbor that is advertising that remote network

Reported/advertised distance : This is the metric of a remote network, as reported by a neighbor.

Neighbor table : Each router keeps state information about adjacent neighbors .

Topology table: It contains all destinations advertised by neighboring routers, holding each destination address and a list of neighbors that have advertised the destination.

The neighbor and topology tables are stored in RAM and maintained through the use of Hello and update packets.

Feasible successor

A feasible successor is a path whose reported distance is less than the feasible distance, and it is considered a backup route. EIGRP will keep up to six feasible successors in the topology table.

Successor :A successor route (think successful!) is the best route to a remote networkand is stored in the routing table.

Reliable Transport Protocol (RTP)

EIGRP uses a proprietary protocol called Reliable Transport Protocol (RTP) to manage the communication of messages between EIGRP-speaking routers.

When EIGRP sends multicast traffic, it uses the Class D address 224.0.0.10. For each multicast EIGRP sends out, it maintains a list of the neighbors who have replied. If EIGRP doesn’t get a reply from a neighbor, it will switch to using unicasts to resend the same data. If it still doesn’t get a reply after 16 unicast attempts, the neighbor is declared dead.

Diffusing Update Algorithm (DUAL)

EIGRP uses Diffusing Update Algorithm (DUAL) for selecting and maintaining the best path to each remote network.

DUAL provides EIGRP with possibly the fastest route convergence time among all protocols.

The key to EIGRP’s speedy convergence is twofold:

First, EIGRP routers maintain a copy of all of their neighbors’ routes, which they use to calculate their own cost to each remote network. If the best path goes down, it examines the contents of the topology table to select the best replacement route.

Second, if there isn’t a good alternative in the local topology table, EIGRP routers ask their neighbors for help finding one.

Using EIGRP to Support Large Networks

EIGRP includes features that make it suitable for use in large networks:

- Support for multiple ASes on a single router

- Support for VLSM and summarization

- Route discovery and maintenance

Multiple ASes

EIGRP uses autonomous system numbers to identify the collection of routers that share route information. Only routers that have the same autonomous system numbers share routes.

it’s possible to divide the network into multiple distinct EIGRP autonomous systems, or ASes. Each AS is populated by a contiguous series of routers, and route information can be shared among the different ASes via redistribution.

VLSM Support and Summarization

EIGRP supports the use of Variable Length Subnet Masks. because the subnet mask is propagated with every route update.

EIGRP also supports the use of discontiguous subnets.

The discontiguous network: is the one that has two or more subnetworks of a Classful network connected together by different classful networks.

Figure 7.1 displays a typical discontiguous network. The subnets 172.16.10.0 and 172.16.20.0 are connected together with a 10.3.1.0 network. By default, each router thinks it has the only 172.16.0.0 classful network.

It’s important to understand that discontiguous networks just won’t work with RIPv1 or IGRP at all. And they don’t work by default on RIPv2 or EIGRP either, but discontiguous networks do work on OSPF networks by default because OSPF does not auto-summarize like EIGRP. But no worries about EIGRP—there are ways to make EIGRP work. I’ll show you how to do that a bit later in this chapter.

EIGRP automatically summarizes networks at their classful boundaries, and Figure 7.2 shows how a router running EIGRP would see the network plus the boundaries that it would auto-summarize.

Route Discovery and Maintenance

EIGRP uses a series of tables to store important information about its environment:

Neighborship table : (usually referred to as the neighbor table) records information about routers with whom neighborship relationships have been formed.

Topology table : stores the route advertisements about every route in the internetwork received from each neighbor.

Route table: stores the routes that are currently used to make routing decisions.

EIGRP Metrics

to compare routes and select the best possible path, EIGRP can use a combination of four:

- Bandwidth

- Delay

- Reliability

- Load

Like IGRP, EIGRP uses only bandwidth and delay of the line to determine the best path to a remote network by default.

there’s a fifth element, maximum transmission unit (MTU) size.

Maximum Paths and Hop Count

By default, EIGRP can provide equal-cost load balancing of up to four links. However, you can have EIGRP actually load-balance across up to six links (equal or unequal) by using the following command:

Pod1R1(config)#router eigrp 10

Pod1R1(config-router)#maximum-paths ?

<1-6> Number of paths

In addition, EIGRP has a maximum hop count of 100, but it can be set up to 255:

Pod1R1(config)#router eigrp 10

Pod1R1(config-router)#metric maximum-hops ?

<1-255> Hop count

Abstract of CCNA study guide-24 - RIP

2011-11-22T22:48:00.001-08:00

Routing Information Protocol (RIP)

- distance-vector routing protocol.

- RIP sends routing table out to all active interfaces every 30 seconds.

- RIP only uses hop count to determine the best way to a remote network

- maximum allowable hop count of 15 (16 unreachable).

- RIP works well in small networks, but it’s inefficient on large networks with slow WAN links or on networks with a large number of routers installed.

- RIP version 1 uses only classful routing, (devices in the network must use the same subnet mask).

- RIP version 2 sends subnet mask information with the route updates( classless routing).

RIP Timers

RIP uses four different kinds of timers to regulate its performance:

Route update timer Sets the interval (typically 30 seconds) between periodic routing updates in which the router sends a complete copy of its routing table out to all neighbors.

Route invalid timer Determines the length of time that must elapse (180 seconds) before a router determines that a route has become invalid.

Holddown timer : Routes will enter into the holddown state when an update packet is received that indicated the route is unreachable. (The default is 180 seconds.)

Route flush timer : Sets the time between a route becoming invalid and its removal from the routing table (240 seconds).

Configuring RIP Routing

Corp#config t

Corp(config)#router rip

Corp(config-router)#network 10.0.0.0

Remember that RIP uses the classful address when configuring the network address. Because of this, all subnet masks must be the same on all devices in the network (this is called classful routing). To clarify this, let’s say you’re using a Class B network address of 172.16.0.0/24 with subnets 172.16.10.0, 172.16.20.0, and 172.16.30.0. You would only type in the classful network address of

172.16.0.0 and let RIP find the subnets and place them in the routing table.

Verifying the RIP Routing Tables

Each routing table should now have all directly connected routes as well as RIP-injected routes received from neighboring routers.

This output shows us the contents of the Corp routing table:

Corp# sh ip route

10.0.0.0/24 is subnetted, 12 subnets

R 10.1.11.0 [120/1] via 10.1.5.2, 00:00:28, Serial0/2/0

R 10.1.10.0 [120/1] via 10.1.5.2, 00:00:28, Serial0/2/0

R 10.1.9.0 [120/1] via 10.1.4.2, 00:00:26, Serial0/1/0

R 10.1.8.0 [120/1] via 10.1.4.2, 00:00:26, Serial0/1/0

R 10.1.12.0 [120/2] via 10.1.5.2, 00:00:28, Serial0/2/0

C 10.1.3.0 is directly connected, Serial0/0/1

C 10.1.2.0 is directly connected, Serial0/0/0

C 10.1.1.0 is directly connected, FastEthernet0/1

R 10.1.7.0 [120/1] via 10.1.3.2, 00:00:07, Serial0/0/1

[120/1] via 10.1.2.2, 00:00:10, Serial0/0/0

R 10.1.6.0 [120/1] via 10.1.3.2, 00:00:07, Serial0/0/1

[120/1] via 10.1.2.2, 00:00:10, Serial0/0/0

C 10.1.5.0 is directly connected, Serial0/2/0

C 10.1.4.0 is directly connected, Serial0/1/0

The R means that the networks were added dynamically using the RIP routing protocol.

The [120/1] is the administrative distance of the route (120) along with the number of hops to that remote network (1).

remember that you configure only the classful network statement, which means you turn all host bits off.

Holding Down RIP Propagations

You probably don’t want your RIP network advertised everywhere on your LAN and WAN.

There’s not a whole lot to be gained by advertising your RIP network to the Internet, now, is there?

to stop unwanted RIP updates from propagating use the passive-interface command

This command prevents RIP update broadcasts from being sent out a specified interface, yet that same interface can still receive RIP updates.

Lab_A#config t

Lab_A(config)#router rip

Lab_A(config-router)#network 192.168.10.0

Lab_A(config-router)#passive-interface serial 0/0

RIP Version 2 (RIPv2)

- Both RIPv1 and RIPv2 are distance-vector protocols

- the timers and loop-avoidance schemes are the same in both RIP versions

- Both RIPv1 and RIPv2 are configured as classful addressing (but RIPv2 is considered classless because subnet information is sent with each route update)

- both have the same administrative distance (120).

Table 6.3 discusses the differences between RIPv1 and RIPv2.

RIPV1	RIPV2
Distance Vector	Distance Vector
Maximum hop count 15	Maximum hop count 15
Classful	Classless
Broadcast based	Multicast 224.0.0.9
No support for VLSM	supports VLSM networks
No authentication	Allow MD5 authentication
No support for discontiguous networks	Supports discontiguous networks

Configuring RIPv2:

Lab_C(config)#router rip

Lab_C(config-router)#network 192.168.40.0

Lab_C(config-router)#network 192.168.50.0

Lab_C(config-router)#version 2

Verifying Your Configurations

The following list includes the commands you can use to verify the routed and routing protocols :

- show ip route (discussed before)

- show ip protocols

- debug ip rip

The show ip protocols Command

The show ip protocols command :shows you the routing protocols that are configured on your router. Looking at the following output, you can see that RIP is running on the router and the timers that RIP uses:

R3#sh ip protocols

Routing Protocol is "rip"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Sending updates every 30 seconds, next due in 24 seconds

Invalid after 180 seconds, hold down 180, flushed after 240

Redistributing: rip

Default version control: send version 1, receive version 1

Interface Send Recv Triggered RIP Key-chain

FastEthernet0/1 1 1

Serial0/0/1 1 1

Automatic network summarization is not in effect

Maximum path: 4

Routing for Networks:

10.0.0.0

Passive Interface(s):

FastEthernet0/0

Serial0/0/0

Routing Information Sources:

Gateway Distance Last Update

10.1.11.2 120 00:00:10

10.1.5.1 120 00:00:22

Distance: (default is 120)

Notice in this output that RIP is sending updates every 30 seconds, which is the default. The timers used in distance vector are also shown.

Notice further down that RIP is routing for directly connected interfaces f0/1 and s0/0/0.

The version is listed to the right of the interfaces—RIPv1.

F0/0 and s0/0/0 are listed as passive interfaces .

The neighbors it found are 10.1.11.2 and 10.1.5.1. The last entry is the default AD for RIP (120).

Troubleshooting with the show ip protocols Command

Let’s use a sample router and use the show ip protocols command :

Router#sh ip protocols

Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 6 seconds

Invalid after 180 seconds, hold down 180, flushed after240

Outgoing update filter list for all interfaces is

Incoming update filter list for all interfaces is

Redistributing: rip

Default version control: send version 1, receive any version

Interface Send Recv Key-chain

Serial0/0 1 1 2

Serial0/1 1 1 2

Routing for Networks:

10.0.0.0

Routing Information Sources:

Gateway Distance Last Update

10.168.11.14 120 00:00:21

Distance: (default is 120)

Let’s also look at the show ip interface brief command from the same router:

Router#sh ip interface brief

Interface IP-Address OK? Method Status

FastEthernet0/0 192.168.18.1 YES manual up

Serial0/0 10.168.11.17 YES manual up

FastEthernet0/1 unassigned YES NRAM Administatively down

Serial0/1 192.168.11.21 YES manual up

Under the show ip protocols output, you can see that we’re using RIP routing for network 10.0.0.0, which means our configuration would look like this:

Router(config)#router rip

Router(config-router)#network 10.0.0.0

Also, only serial 0/0 and serial 0/1 are participating in the RIP network. And last, our neighbor router is 10.168.11.14.

From the output of the show ip interface brief command, you can see that only serial 0/0 is in the 10.0.0.0 network. This means that the router will only send and receive routing updates with the 10.0.0.0 network and not advertise the 192.168.0.0 networks out any interface.

The debug ip rip Command

The debug ip rip command sends routing updates as they are sent and received on the router to the console session. If you are telnetted into the router, you’ll need to use the terminal monitor command to be able to receive the output from the debug commands.

R3#debug ip rip

RIP protocol debugging is on

R3#terminal monitor

*Mar 17 19:08:34.371: RIP: sending v1 update to 255.255.255.255 via Serial0/0/1 (10.1.5.2)

*Mar 17 19:08:34.371: RIP: build update entries

*Mar 17 19:08:34.371: subnet 10.1.10.0 metric 1

*Mar 17 19:08:34.371: subnet 10.1.11.0 metric 1

*Mar 17 19:08:34.371: subnet 10.1.12.0 metric 2

*Mar 17 19:08:40.107: RIP: received v1 update from 10.1.5.1 on Serial0/0/1

*Mar 17 19:08:40.107: 10.1.1.0 in 1 hops

*Mar 17 19:08:40.107: 10.1.2.0 in 1 hops

*Mar 17 19:08:40.107: 10.1.3.0 in 1 hops

*Mar 17 19:08:40.107: 10.1.4.0 in 1 hops

*Mar 17 19:08:40.107: 10.1.6.0 in 2 hops

*Mar 17 19:08:40.107: 10.1.7.0 in 2 hops

*Mar 17 19:08:40.107: 10.1.8.0 in 2 hops

*Mar 17 19:08:40.107: 10.1.9.0 in 2 hops

Troubleshooting with the debug ip rip Command

Now let’s use the debug ip rip command to both discover a problem and figure out how RIP was configured on a router from a different sample network:

07:12:58: RIP: sending v1 update to 255.255.255.255 via FastEthernet0/0 (172.16.1.1)

07:12:58: network 10.0.0.0, metric 1

07:12:58: network 192.168.1.0, metric 2

07:12:58: RIP: sending v1 update to 255.255.255.255 via Serial0/0 (10.0.8.1)

07:12:58: network 172.16.0.0, metric 1

07:12:58: RIP: Received v1 update from 10.0.15.2 n Serial0/0

07:12:58: 192.168.1.0 in one hop

07:12:58: 192.168.168.0 in 16 hops (inaccessible)

You can see from the updates that we’re sending out information about networks 10.0.0.0, 192.168.1.0, and 172.16.0.0. But both the 10.0.0.0 network and the 172.16.0.0 network are being advertised with a hop count (metric) of 1, meaning that these networks are directly connected. The 192.168.1.0 is being advertised as a metric of 2, which means that it is not directly connected.

For this to be happening, our configuration would have to look like this:

Router(config)#router rip

Router(config-router)#network 10.0.0.0

Router(config-router)#network 172.16.0.0

And there’s something else you can find out by looking at this: There are at least two routers participating in the RIP network because we’re sending out two interfaces but only receiving RIP updates on one interface. Also, notice that the network 192.168.168.0 is being advertised as 16 hops away. RIP has a maximum hop count of 15, so 16 is considered unreachable, making this network inaccessible.

I have one more output I want to show you—see if you can find the problem. Both a debug ip rip and a show ip route output are shown from our sample router:

07:12:56: RIP: received v1 update from 172.16.100.2 on Serial0/0

07:12:56: 172.16.10.0 in 1 hops

07:12:56: 172.16.20.0 in 1 hops

07:12:56: 172.16.30.0 in 1 hops

Router#sh ip route

[output cut]

Gateway of last resort is not set

172.16.0.0/24 is subnetted, 8 subnets

C 172.16.150.0 is directly connected, FastEthernet0/0

C 172.16.220.0 is directly connected, Loopback2

R 172.16.210.0 is directly connected, Loopback1

R 172.16.200.0 is directly connected, Loopback0

R 172.16.30.0 [120/2] via 172.16.100.2, 00:00:04, Serial0/0

S 172.16.20.0 [120/2] via 172.16.150.15

R 172.16.10.0 [120/2] via 172.16.100.2, 00:00:04, Serial0/0

R 172.16.100.0 [120/2] is directly connected, Serial0/0

Looking at the two outputs, can you tell why users can’t access 172.16.20.0?

The debug output shows that network 172.16.20.0 is one hop away and being received on serial0/0 from 172.16.100.2. By checking out the show ip route output, you can see that packets with a destination of 172.16.20.0 are being sent to 172.16.150.15 because of a static route. The output also shows that 172.16.150.0 is directly connected to FastEthernet 0/0 and network 172.16.20.0 is out serial 0/0.

Abstract of CCNA study guide-23 - IP Routing 2

2011-11-22T22:42:00.001-08:00

Dynamic Routing

Two types of routing protocols are used in internetworks: interior gateway protocols (IGPs) and exterior gateway protocols (EGPs).

IGPs are used to exchange routing information with routers in the same autonomous system (AS).

EGPs are used to communicate between ASes.

Routing Protocol Basics

There are some important things you should know about routing protocols before getting

deeper into RIP. Specifically, you need to understand administrative distances, the three different

kinds of routing protocols, and routing loops.

Administrative Distances

- The administrative distance (AD): is used to rate the trustworthiness of routing information received on a router from a neighbor router.

- An administrative distance is an integer from 0 to 255, where 0 is the most trusted and 255 means no traffic will be passed via this route.

- If a router receives two updates listing the same remote network, the router check First the AD. If one of the advertised routes has a lower AD than the other, then the route with the lowest AD will be placed in the routing table.

- If both advertised routes to the same network have the same AD, then routing protocol metrics (such as hop count or bandwidth of the lines) will be used to find the best path to the remote network.

- The advertised route with the lowest metric will be placed in the routing table. But if both advertised routes have the same AD as well as the same metrics, then the routing protocol will load-balance to the remote network (which means that it sends packets

- down each link).

TABLE 6 . 2 Default Administrative Distances

Route Source	Default AD
Connected interface	0
Static route	1
EIGRP	90
IGRP	100
OSPF	110
RIP	120
External EIGRP	170

Routing Protocols

There are three classes of routing protocols:

Distance vector : that find the best path to a remote network by judging distance.

Each time a packet goes through a router, that’s called a hop. The route with the least number of hops to the network is determined to be the best route.

Both RIP and IGRP are distance-vector routing protocols.

Link state : each router create three separate tables.

Neighbors: keeps track of directly attached neighbors

Topology : determines the topology of the entire internetwork

Routing table :

OSPF is an IP routing protocol that is completely link state.

Hybrid Hybrid protocols use aspects of both distance vector and link state—for example, EIGRP.

Distance-Vector Routing Protocols

The distance-vector routing algorithm passes complete routing table contents to neighboring

routers, which then combine the received routing table entries with their own routing tables to

complete the router’s routing table.

Routing Loops

- the slow convergence of distance-vector routing protocols can result in inconsistent routing tables and routing loops.

- Routing loops can occur because every router isn’t updated simultaneously.

Example: let’s say that the interface to Network 5 in Figure 6.15 fails. All routers know about Network 5 from RouterE. RouterA, in its tables, has a path to Network 5 through

RouterB.

When Network 5 fails, RouterE tells RouterC. But routers A, B, and D don’t know about Network 5 yet, so they

keep sending out update information. RouterC will eventually send out its update and cause B to stop routing to Network 5, but routers A and D are still not updated. To them, it appears that Network 5 is still available through RouterB with a metric of 3.

The problem occurs when RouterA sends out its regular route table which includes the ability to reach Network 5, and now routers B and D receive that Network 5 can be reached from RouterA, so routers B and D then send out the information that Network 5 is available. Any packet destined for Network 5 will go to RouterA, to RouterB, and then back to RouterA. This is a routing loop—how do you stop it?

Maximum Hop Count

One way of solving this problem is to define a maximum hop count. RIP permits a hop count of up to 15, so anything that requires 16 hops is deemed unreachable.

Split Horizon

enforcing the rule that routing information cannot be sent back in the direction from which it was received.

Route Poisoning

For example, when Network 5 goes down, RouterE initiates route poisoning by advertising Network 5 as 16, or unreachable

This poisoning of the route to Network 5 keeps RouterC from being susceptible to incorrect updates about the route to Network 5. When RouterC receives a route poisoning from RouterE, it sends an update, called a poison reverse, back to RouterE. This ensures that all routes on the segment have received the poisoned route information.

Holddowns

A holddown prevents regular update messages from reinstating a route that is going up and down (called flapping).

Abstract of CCNA study guide-22 - IP Routing 1

2011-11-22T22:29:00.001-08:00

IP Routing

IP routing: is the process of moving packets from one network to another network using routers.

A routing protocol: is used by routers to dynamically

1) find all the networks in the internetwork

2) ensure that all routers have the same routing table.

3) determines the path of a packet through an internetwork..

Examples of routing protocols are RIP, RIPv2, EIGRP, and OSPF.

A routed protocol: Used to send user data (packets) through the established enterprise. Routed protocols are assigned to an interface and determine the method of packet delivery.

Examples of routed protocols are IP and IPv6.

Routing Basics

The term routing is used for taking a packet from one device and sending it through the network to another device on a different network.

Routers don’t really care about hosts— they only care about networks and the best path to each network. The logical network address of the destination host is used to get packets to a network through a routed network,

and then the hardware address of the host is used to deliver the packet from a router to the correct destination host.

To be able to route packets, a router must know, at a minimum, the following:

- Destination address

- Neighbor routers from which it can learn about remote networks

- Possible routes to all remote networks

- The best route to each remote network

- How to maintain and verify routing information

If a network is directly connected, then the router already knows how to get to it.

If a network isn’t directly connected to the router, the router must use one of two ways to

learn how to get to the remote network: static routing or dynamic routing

Static Routing : someone must hand-type all network locations into the routing table

dynamic routing: a protocol on one router communicates with the same protocol running on neighbor routers. The routers then update each other about all the networks they know about and place this information into the routing table.

The IP Routing Process

- You must know that the frame changes at each hop but the packet is never changed in any way until it reaches the destination device.

- The MAC addresses are always local. A MAC (hardware) address will only be used on a local LAN. It will never pass a router’s interface.

- Understand that a frame carries a packet to only two places. A frame uses MAC (hardware) addresses to send a packet on a LAN. The frame will take the packet to either a host on the LAN or a router’s interface if the packet is destined for a remote network

Configuring IP Routing in Our Network

You’ll learn about the following types of routing in the following sections:

_ Static routing

_ Default routing

_ Dynamic routing

Static Routing

Static routing has the following benefits:

_ There is no overhead on the router CPU.

_ There is no bandwidth usage between routers.

_ It adds security because the administrator can choose to allow routing access to certain networks only.

Static routing has the following disadvantages:

_ The administrator must understand the internetwork and how each router is connected in order to configure routes correctly.

_ If a network is added , the administrator has to add a route to it on all routers by hand.

_ It’s not feasible in large networks.

syntax for static route :

ip route [destination _network ] [mask ] [next –hop-address or exit interface ] [administrative_distance] [permanent]

This list describes each command in the string:

destination _network : The network you’re placing in the routing table.

Mask: The subnet mask being used on the network.

next –hop-address : The address of the next-hop router that will receive the packet .

exit interface : Used in place of the next-hop address , and shows up as a directly connected route.

administrative_distance : By default, static routes have an administrative distance of 1 (or even 0 if you use an exit interface instead of a next-hop address). You can change the default value by adding an administrative weight at the end of the command.

Permanent: keeps the entry in the routing table no matter what happens.

Example

Router(config)#ip route 172.16.3.0 255.255.255.0 192.168.2.4

Router(config)#ip route 172.16.3.0 255.255.255.0 192.168.2.4 150

Router(config)#ip route 172.16.3.0 255.255.255.0 s0/0/0

Verifying Your Configuration

Sh ip route command:

View the IP routing tables created on a Cisco router

Ex:

Corp#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS

level-2, ia - IS-IS inter area, * - candidate default, U - per-user

static route, o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, FastEthernet0/1

Corp#

Ping Command:

I’ll start by pinging from the 1242AP to the 871W router.

Ex:

871W# ping 10.1.1.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

Trace Command:

we can trace from the 871W router to see the hops the packet takes to get to HostA:

871W#trace 10.1.6.2

Type escape sequence to abort.

Tracing the route to 10.1.6.2

1 10.1.11.1 0 msec 0 msec 0 msec

2 10.1.5.1 4 msec 0 msec 4 msec

3 10.1.2.2 0 msec 0 msec 4 msec

4 10.1.6.2 4 msec 4 msec *

Default Routing

- We use default routing to send packets with a remote destination network not in the routing table to the next-hop router.

- You should only use default routing on stub networks—those with only one exit path out of the network..

Configure default route :

we use wildcards in the network address and mask locations of a static route .

871W(config)#ip route 0.0.0.0 0.0.0.0 10.1.11.1

871W(config)#ip classless

871W(config)#do show ip route

Gateway of last resort is 10.1.11.1 to network 0.0.0.0

10.0.0.0/24 is subnetted, 2 subnets

C 10.1.11.0 is directly connected, Vlan1

C 10.1.12.0 is directly connected, Dot11Radio0

S* 0.0.0.0/0 [1/0] via 10.1.11.1

871W(config)#

An S*, indicates that this entry is for a default route.

I could have completed the default route command another way:

871W(config)#ip route 0.0.0.0 0.0.0.0 vlan1

What this is telling us is that if you don’t have an entry for a network in the routing table, just

forward it out VLAN1 .

Here are three commands for adding a gateway of last resort on the gateway router to the ISP.

Gateway(config)#ip route 0.0.0.0 0.0.0.0 217.124.6.1

Gateway(config)#ip route 0.0.0.0 0.0.0.0 s0/0

Gateway(config)#ip default-network 217.124.6.0

all three of these commands would accomplish the goal of setting the gateway of last resort, but there are some small differences between them.

- First, the exit interface solution would be used over the other two solutions because it has an AD of 0.

- Also, the ip default-network command would advertise the default network when you configure an IGP

(like RIP) on the router. This is so other routers in your internetwork will receive this route as a default route automatically.

Problems:

Problem1: But what happens if you misconfigured a default route? look at the output of a show ip route command and next Figure :

Router#sh ip route

[output cut]

Gateway of last resort is 172.19.22.2 to network 0.0.0.0

C 172.17.22.0 is directly connected, FastEthernet0/0

C 172.18.22.0 is directly connected, Serial0/0

S* 0.0.0.0/0 [1/0] via 172.19.22.2

the WAN link is on network 172.18.22.0 and the default route is forwarding all packets to the 172.19.22.0 network. This is just bad—it will never work, so the problem is a misconfigured static (default) route.

Problem2: If you have the routing table as shown in the following lines, what happens if the router receives a packet from 10.1.6.100 destined for host 10.1.8.5?

Corp#sh ip route

[output cut]

Gateway of last resort is 10.1.5.5 to network 0.0.0.0

R 10.1.3.0 [120/1] via 101.2.2, 00:00:00, Serial 0/0

C 10.1.2.0 is directly connected, Serial0/0

C 10.1.5.0 is directly connected, Serial0/1

C 10.1.6.0 is directly connected, Fastethernet0/0

R* 0.0.0.0/0 [120/0] via 10.1.5.5, 00:00:00 Serial 0/1

the default route is listed as R*, which means it’s a RIP-injected route. This is because someone configured the ip default-network command on a remote router as well as configuring RIP, causing RIP to advertise this route through the internetwork as a default route. Since the destination address is 10.1.8.5 and there is no route to network 10.1.8.0, the router would use the default route and send the packet out serial 0/1.

video:ccna IP Addressing

2011-11-22T12:37:00.001-08:00

Cisco Training CCNA IP Addressing - Part 1 of 5

Cisco Training CCNA IP Addressing - Part 2 of 5

Cisco Training CCNA IP Addressing - Part 3 of 5

Cisco Training CCNA IP Addressing - Part 4 of 5

Cisco Training CCNA IP Addressing - Part 5 of 5

CCIE R&S List of Books

2011-11-22T01:16:00.001-08:00

CCIE R&S Reading List

Abstract of CCNA study guide-21 - Checking Connectivity and Troubleshooting

2011-11-21T02:07:00.001-08:00

Checking Network Connectivity and Troubleshooting

You can use the ping and traceroute commands to test connectivity to remote devices, and both of them can be used with many protocols, not just IP. But don’t forget that the show ip route command is a good troubleshooting command for verifying your routing table and the show interfaces command will show you the status of each interface.

Debugging

Debug is a troubleshooting command that’s available from the privileged exec mode of Cisco IOS. It’s used to display information about various router operations and the related traffic generated or received by the router, plus any error messages.

you really need to understand some important facts about its use:

Debug is regarded as a very high-priority task because it can consume a huge amount of resources and the router is forced to process-switch the packets being debugged. So you don’t just use debug as a monitoring tool—it’s meant to be used for a short period of time and only as a troubleshooting tool.

it’s best to use more-specific debug commands.

As you can see from the following output, you can’t enable debugging from user mode, only

privileged mode:

Corp>debug ?

% Unrecognized command

Corp>en

Corp#debug all

This may severely impact network performance. Continue? (yes/[no]):yes

All possible debugging has been turned on

2d20h: SNMP: HC Timer 824AE5CC fired

2d20h:

2d20h: Rudpv1 Sent: Pkts 0, Data Bytes 0, Data Pkts 0

2d20h: Rudpv1 Discarded: 0, Retransmitted 0

Corp#

To disable debugging on a router, just use the command no in front of the debug command:

Corp#no debug all

But I typically just use the undebug all command since it is so easy when using the shortcut:

Corp#un all

Remember that instead of using the debug all command, it’s almost always better to use specific commands—and only for short periods of time.

Corp#debug ip rip

RIP protocol debugging is on

Corp#

1w4d: RIP: sending v2 update to 224.0.0.9 via Serial0/0 (192.168.12.1)

1w4d: RIP: build update entries

1w4d: 10.10.10.0/24 via 0.0.0.0, metric 2, tag 0

Corp#un all

Using the show processes Command

the show processes (or show processes cpu) is a good tool for determining a given router’s CPU utilization. Plus, it’ll give you a list of active processes along with their corresponding process ID, priority, scheduler test (status), CPU time used, number of times invoked, and so on.

this command is super handy when you want to evaluate your router’s performance and CPU utilization.

Corp#sh processes

CPU utilization for five seconds: 2%/0%; one minute: 0%; five minutes: 0%

PID QTy PC Runtime (ms) Invoked uSecs Stacks TTY Process

1 Cwe 8034470C 0 1 0 5804/6000 0 Chunk Manager

6 Cwe 80355E5C 20 3 6666 5704/6000 0 Pool Manager

[output cut]

So basically, the output from the show processes command shows that our router is happily able to process debugging commands without being overloaded.

Abstract of CCNA study guide-20 - Resolving Hostnames

2011-11-21T02:06:00.001-08:00

To use a hostname rather than an IP address to connect to a remote device, the device that you are using to make the connection must be able to translate the hostname to an IP address.

There are two ways to resolve hostnames to IP addresses: building a host table on each router or building a Domain Name System (DNS) server.

Building a Host Table

A host table provides name resolution only on the router that it was built upon. The command to build a host table on a router is as follows: ip host host_name tcp_port_number ip_address

The default is TCP port number 23, but you can create a session using Telnet with a different TCP port number if you want. You can also assign up to eight IP addresses to a hostname.

Here’s an example of configuring a host table on the Corp router with two entries to resolve the names for the R1 router and the ap device:

Corp#config t

Corp(config)#ip host R1 10.2.2.2

Corp(config)#ip host ap 10.1.1.2

Notice in the above router configuration that I can just keep adding IP addresses to reference a host, one after another, up to eight IP address. And to see the built host table, just use the show hosts command:

Corp(config)#do show hosts

Default domain is not set

Name/address lookup uses domain service

Name servers are 255.255.255.255

Codes: UN - unknown, EX - expired, OK - OK, ?? – revalidate ,temp - temporary, perm - permanent

NA - Not Applicable None - Not defined

Host Port Flags Age Type Address(es)

ap None (perm, OK) 0 IP 10.1.1.2

R1 None (perm, OK) 0 IP 10.2.2.2

Corp(config)#^Z

Corp#

You can see the two hostnames plus their associated IP addresses in the preceding router output. The perm in the Flags column means that the entry is manually configured. If it said temp, it would be an entry that was resolved by DNS.

To verify that the host table resolves names, try typing the hostnames at a router prompt. Remember that if you don’t specify the command, the router assumes you want to telnet.

In the following example, I’ll use the hostnames to telnet into the remote devices and press

Ctrl+Shift+6 and then X to return to the main console of the Corp router:

Corp#r1

Trying R1 (10.2.2.2)... Open

User Access Verification

Password:

R1>Ctrl+Shift+6

Corp#ap

Trying ap (10.1.1.2)... Open

User Access Verification

Password:

ap>Ctrl+Shift+6

Corp#

Notice that the entries in the show sessions output now display the hostnames and IP addresses instead of just the IP addresses:

Corp#sh sessions

Conn Host Address Byte Idle Conn Name

1 r1 10.2.2.2 0 1 r1

* 2 ap 10.1.1.2 0 0 ap

Corp#

If you want to remove a hostname from the table, just use the no ip host command like this:

RouterA(config)#no ip host R1

The problem with the host table method is that you would need to create a host table on each router to be able to resolve names. And if you have a whole bunch of routers, using DNS is a much better choice!

Using DNS to Resolve Names

Any time a Cisco device receives a command it doesn’t understand, it will try to resolve it through DNS by default. Watch what happens when I type the special command todd at a Cisco router prompt:

Corp#todd

Translating “todd”...domain server (255.255.255.255)

% Unknown command or computer name, or unable to find

computer address

Corp#

It doesn’t know my name or what command I am trying to type, so it tries to resolve this through DNS. This is really annoying because I need to wait for the name lookup to time out.

You can prevent a time-consuming DNS lookup by using the no ip domain-lookup command on your router from global configuration mode.

If you have a DNS server on your network, you need to add a few commands to make DNS name resolution work:

- The first command is ip domain-lookup, which is turned on by default.

_ The second command is ip name-server. This sets the IP address of the DNS server. You can enter the IP addresses of up to six servers.

_ The last command is ip domain-name. Although this command is optional, it really should be set.

Here’s an example of using these three commands:

Corp#config t

Corp(config)#ip domain-lookup

Corp(config)#ip name-server 192.168.0.70

Corp(config)#ip domain-name lammle.com

After the DNS configurations are set, you can test the DNS server by using a hostname to ping or telnet a device like this:

Corp#ping R1

use the show hosts command to see that the device cached this information in the host table:

Corp#sh hosts

Default domain is lammle.com

Name/address lookup uses domain service

Name servers are 192.168.0.70

Host Flags Age Type Address(es)

R1 (temp, OK) 0 IP 10.2.2.2

ap (perm, OK) 0 IP 10.1.1.2

Corp#

The entry that was resolved is shown as temp, but the ap device is still perm, meaning that it’s a static entry. Notice that the hostname is a full domain name. If I hadn’t used the ip domain-name lammle.com command, I would have needed to type in ping r1.lammle.com, which is a pain.

Abstract of CCNA study guide-19 -Documenting a Network Topology Using CDP

2011-11-21T02:04:00.001-08:00

Documenting a Network Topology Using CDP

You can determine the router types, interface types, and IP addresses of various interfaces using only CDP commands and the show running-config command.

Using Telnet

Telnet, part of the TCP/IP protocol suite, is a virtual terminal protocol that allows you to make connections to remote devices, gather information, and run programs.

You run the Telnet program by typing telnet from any command prompt (DOS or Cisco). You need

to have VTY passwords set on the routers for this to work. Remember, you can’t use CDP to gather information about routers and switches that aren’t directly connected to your device. But you can use the Telnet application to connect to your neighbor devices and then run CDP on those remote devices to get information on them.

You can issue the telnet command from any router prompt like this:

Corp#telnet 10.2.2.2

Trying 10.2.2.2 ... Open

Password required, but none set

[Connection to 10.2.2.2 closed by foreign host]

Corp#

On a Cisco router, you don’t need to use the telnet command; you can just type in an IP address from a command prompt Here’s how that looks using just the IP address:

Corp#10.2.2.2

Trying 10.2.2.2 ... Open

Password required, but none set

[Connection to 10.2.2.2 closed by foreign host]

Corp#

Now set VTY passwords on the router I want to telnet into (chapter4).

Now let’s try this again:

Corp#10.2.2.2

Trying 10.2.2.2 ... Open

User Access Verification

Password:

R1>

Remember that the VTY password is the user-mode password, not the enable-mode password. Watch what happens when I try to go into privileged mode after telnetting into router R1:

R1>en

% No password set

R1>

It is basically saying, “No way!” This is a really good security feature because you don’t want anyone telnetting into your device and being able to just type the enable command to get into privileged mode. You’ve got to set your enable-mode password or enable secret password to use Telnet to configure remote devices!

Telnetting into Multiple Devices Simultaneously

If you telnet to a router or switch, you can end the connection by typing exit at any time. But what if you want to keep your connection to a remote device but still come back to your original router console? To do that, you can press the Ctrl+Shift+6 key combination, release it, and then press X.

Here’s an example of connecting to multiple devices from my Corp router console:

Corp#10.2.2.2

Trying 10.2.2.2 ... Open

User Access Verification

Password:

R1>Ctrl+Shift+6

Corp#

In this example, I telnetted to the R1 router and then typed the password to enter user mode.I next pressed Ctrl+Shift+6, then X (but you can’t see that because it doesn’t show on the screen output). Notice that my command prompt is now back at the Corp router.

Checking Telnet Connections

To see the connections made from your router to a remote device, use the show sessions command:

Corp#sh sessions

Conn Host Address Byte Idle Conn Name

1 10.2.2.2 10.2.2.2 0 0 10.2.2.2

* 2 10.1.1.2 10.1.1.2 0 0 10.1.1.2

Corp#

See that asterisk (*) next to connection 2? It means that session 2 was your last session. You can return to your last session by pressing Enter twice. You can also return to any session by typing the number of the connection and pressing Enter.

Checking Telnet Users

You can list all active consoles and VTY ports in use on your router with the show users command:

Corp#sh users

Line User Host(s) Idle Location

* 0 con 0 10.1.1.2 00:00:01

10.2.2.2 00:01:06

In the command’s output, con represents the local console. In this example, the console is connected

to two remote IP addresses, or in other words, two devices.

Closing Telnet Sessions

You can end Telnet sessions by typing exit or disconnect.

To end a session from a remote device, use the exit command:

ap>exit

[Connection to 10.1.1.2 closed by foreign host]

Corp#

To end a session from a local device, use the disconnect command:

Corp#sh session

Conn Host Address Byte Idle Conn Name

2 10.2.2.2 10.2.2.2 0 0 10.2.2.2

Corp#disconnect 2

Closing connection to 10.2.2.2 [confirm][enter]

Corp#

In this example, I used the session number 2 because that was the connection to the R1 router that I wanted to end. As I showed, you can use the show sessions command to see the connection number.

Notice the show users command :

R1#sh users

Line User Host(s) Idle Location

* 0 con 0 idle 00:00:00

vty 194 idle 00:00:21 10.2.2.1

This output shows that VTY has IP address 10.2.2.1 connected. That’s the Corp router. Also notice that the Corp router connected to line 194—remember, you cannot choose which line you connect to! This is why we set the same password on all lines. To clear the connection, use the clear line # command:

R1#clear line 194

[confirm][enter]

[OK]

R1#sh users

Line User Host(s) Idle Location

* 0 con 0 idle 00:00:00

This output confirms that the line has been cleared.

Abstract of CCNA study guide-18 - CDP

2011-11-21T02:02:00.001-08:00

Using Cisco Discovery Protocol (CDP)

Cisco Discovery Protocol (CDP) is a proprietary protocol designed by Cisco to help administrators collect information about both locally attached and remote devices.

By using CDP, you can gather hardware and protocol information about neighbor devices, which is useful info for troubleshooting and documenting the network.

Getting CDP Timers and Holdtime Information

The show cdp command (sh cdp for short) gives you information about two CDP global parameters that can be configured on Cisco devices:

- CDP timer is how often CDP packets are transmitted out all active interfaces.

-CDP holdtime is the amount of time that the device will hold packets received from neighbor devices.

Both Cisco routers and Cisco switches use the same parameters.

The output on the Corp router looks like this:

Corp#sh cdp

Global CDP information:

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Sending CDPv2 advertisements is enabled

Use the global commands cdp holdtime and cdp timer to configure the CDP holdtime and timer on a router:

Corp(config)#cdp holdtime ?

<10-255> Length of time (in sec) that receiver must keep this packet

Corp(config)#cdp timer ?

<5-254> Rate at which CDP packets are sent (in sec)

You can turn off CDP completely with the no cdp run command from the global configuration mode of a router. To turn CDP off or on for an interface, use the no cdp enable and cdp enable commands.

Gathering Neighbor Information

The show cdp neighbor command (sh cdp nei for short) delivers information about directly connected devices. It’s important to remember that CDP packets aren’t passed through a Cisco switch and that you only see what’s directly attached. So this means that if your router is connected to a switch, you won’t see any of the devices hooked up to that switch.

The following output shows the show cdp neighbor command used on my ISR router:

Corp#sh cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID

ap Fas 0/1 165 T I AIR-AP124 Fas 0

R2 Ser 0/1/0 140 R S I 2801 Ser 0/2/0

R3 Ser 0/0/1 157 R S I 1841 Ser 0/0/1

R1 Ser 0/2/0 154 R S I 1841 Ser 0/0/1

R1 Ser 0/0/0 154 R S I 1841 Ser 0/0/0

Corp#

Okay, we are directly connected with a console cable to the Corp ISR router, and the router is directly connected to four devices. We have two connections to the R1 router.

Table 5.5 summarizes the information displayed by the show cdp neighbor command for each device.

TABLE 5 . 5 Output of the show cdp neighbor Command

Field	Description
Device ID	The hostname of the device directly connected.
Local Interface	The port or interface on which you are receiving the CDP packet.
Holdtime	The amount of time the router will hold the information before discarding it if no more CDP packets are received.
Capability	The capability of the neighbor, such as the router, switch, or repeater. The capability codes are listed at the top of the command output.
Platform	The type of Cisco device directly connected.
Port ID	The neighbor device’s port or interface on which the CDP packets are multicast.

Another command is the show cdp neighbors detail command (show cdp nei de for short). This command can be run on both routers and switches, and it displays detailed information about each device connected

to the device you’re running the command on. Check out this router output for an example:

Corp#sh cdp neighbors detail

Device ID: R2

Entry address(es):

IP address: 10.4.4.2

Platform: Cisco 2801, Capabilities: Router Switch IGMP

Interface: Serial0/1/0, Port ID (outgoing port): Serial0/2/0

Holdtime : 135 sec

Version :

Cisco IOS Software, 2801 Software (C2801-ADVENTERPRISEK9-M),

Experimental Version 12.4(20050525:193634) [jezhao-ani 145]

Compiled Fri 27-May-05 23:53 by jezhao

advertisement version: 2

VTP Management Domain: ‘‘

-------------------------

[output cut]

What are we being shown here? First, we’re given the hostname and IP address of all directly connected devices. In addition to the same information displayed by the show cdp neighbor command (see Table 5.5), the show cdp neighbor detail command gives us the IOS version of the neighbor device.

Note: Remember that you can see the IP address of only directly connected devices.

The show cdp entry * command displays the same information as the show cdp neighbors detail command. Here’s an example of the router output using the show cdp entry * command:

Corp#sh cdp entry *

Device ID: R2

Entry address(es):

IP address: 10.4.4.2

Platform: Cisco 2801, Capabilities: Router Switch IGMP

--More—

[output cut]

There isn’t any difference between the show cdp neighbors detail and show cdp entry * commands. However, the sh cdp entry * command has two options that the show cdp neighbors detail command does not:

Corp#show cdp entry * protocols

Protocol information for ap :

IP address: 10.1.1.2

Protocol information for R2 :

IP address: 10.4.4.2

Protocol information for R3 :

IP address: 10.5.5.1

Protocol information for R1 :

IP address: 10.3.3.2

Protocol information for R1 :

IP address: 10.2.2.2

the show cdp entry * protocols command show the IP addresses of each directly connected neighbor.

The show cdp entry * version show you only the IOS version of your directly connected neighbors:

Corp#show cdp entry * version

Version information for ap :

Cisco IOS Software, C1240 Software (C1240-K9W7-M), Version

12.3(8)JEA, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Compiled Wed 23-Aug-06 16:45 by kellythw

Version information for R2 :

Cisco IOS Software, 2801 Software (C2801-ADVENTERPRISEK9-M),

Experimental Version 12.4(20050525:193634) [jezhao-ani 145]

Compiled Fri 27-May-05 23:53 by jezhao

[output cut]

Although the show cdp neighbors detail and show cdp entry commands are very similar, the show cdp entry command allows you to display only one line of output for each directly connected neighbor, whereas the show cdp neighbor detail command does not. Next, let’s look at the show cdp traffic command.

Gathering Interface Traffic Information

The show cdp traffic command displays information about interface traffic, including the number of CDP packets sent and received and the errors with CDP.

Corp#sh cdp traffic

CDP counters :

Total packets output: 911, Input: 524

Hdr syntax: 0, Chksum error: 0, Encaps failed: 2

No memory: 0, Invalid packet: 0, Fragmented: 0

CDP version 1 advertisements output: 0, Input: 0

CDP version 2 advertisements output: 911, Input: 524

Corp#

Gathering Port and Interface Information

The show cdp interface command gives you the CDP status on router interfaces or switch ports. you can turn off CDP completely on a router by using the no cdp run command. you can also turn off CDP on interface with the no cdp enable command. You enable a port with the cdp enable command. All ports and interfaces default to cdp enable.

On a router, the show cdp interface command displays information about each interface

using CDP, including the encapsulation on the line, the timer, and the holdtime for each interface.

Corp#sh cdp interface

FastEthernet0/0 is administratively down, line protocol is down

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

FastEthernet0/1 is up, line protocol is up

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

Serial0/0/0 is up, line protocol is up

Encapsulation HDLC

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

The above output tells you the interface’s status. To turn off CDP on one interface on a router, use the no cdp enable command from interface configuration mode:

Corp#config t

Corp(config)#int s0/0/0

Corp(config-if)#no cdp enable

Corp(config-if)#do show cdp interface

that serial 0/0/0 while not listed in the router output. To get that output, you’d have to perform a cdp enable on serial 0/0/0. It would then show up in the output:

Corp(config-if)#cdp enable

Abstract of CCNA study guide-17 -Backup and Restore Cisco IOS

2011-11-21T01:59:00.001-08:00

Backing Up and Restoring the Cisco IOS

before you back up an IOS image to a network server on your intranet, you’ve got to do these three things:

- Make sure you can access the network server.

- Ensure that the network server has adequate space for the code image.

- Verify the file naming and path requirement.

And if you have a workstation’s Ethernet port directly connected to a router’s Ethernet interface, you need to verify the following before attempting to copy the image to or from the router:

- TFTP server software must be running on the administrator’s workstation.

- The Ethernet connection between the router and the workstation must be made with a crossover cable.

- The workstation must be on the same subnet as the router’s Ethernet interface.

- The copy flash tftp command must be supplied the IP address of the workstation.

_ And if you’re copying “into” flash, you need to verify that there’s enough room in flash memory

Verifying Flash Memory

Before you attempt to upgrade the Cisco IOS on your router with a new IOS file, you should verify that your flash memory has enough room to hold the new image by using the show flash command (sh flash):

Router#sh flash

-#- --length-- -----date/time------ path

1 21710744 Jan 2 2007 22:41:14 +00:00 c2800nm-advsecurityk9-mz.124-12.bin

[output cut]

32989184 bytes available (31027200 bytes used)

The ISR router above has 64MB of RAM, and half of the memory is in use.

To know The amount of flash use the show version command on the ISR routers:

Router#show version

[output cut]

DRAM configuration is 64 bits wide with parity enabled.

239K bytes of non-volatile configuration memory.

62720K bytes of ATA CompactFlash (Read/Write)

the amount of flash is 64MB.

Notice that the filename in this example is c2800nm-advsecurityk9-mz.124-12.bin.

The main difference in the output of the show flash and show version commands is that the show flash command displays all files in flash and the show version command shows the actual name of the file that the router is using to run the router.

Backing Up the Cisco IOS

To back up the Cisco IOS to a TFTP server, you use the copy flash tftp command.

Router#copy flash tftp

Source filename []?c2800nm-advsecurityk9-mz.124-12.bin

Address or name of remote host []?1.1.1.2

Destination filename [c2800nm-advsecurityk9-mz.124-12.bin]?[enter]

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!

21710744 bytes copied in 60.724 secs (357532 bytes/sec)

Router#

Just copy the IOS filename from either the show flash or show version command and then paste it when prompted for the source filename.

Restoring or Upgrading the Cisco Router IOS

You can download the file from a TFTP server to flash memory by using the copy tftp flash command. make sure the file you want to place in flash memory is in the default TFTP directory on your host.

Router#copy tftp flash

Address or name of remote host []?1.1.1.2

Source filename []?c2800nm-advsecurityk9-mz.124-12.bin

Destination filename [c2800nm-advsecurityk9-mz.124-12.bin]?[enter]

Accessing tftp://1.1.1.2/c2800nm-advsecurityk9-mz.124-12.bin...

Loading c2800nm-advsecurityk9-mz.124-12.bin from 1.1.1.2 (via

FastEthernet0/0):

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[OK - 21710744 bytes]

21710744 bytes copied in 82.880 secs (261954 bytes/sec)

Router#

Backing Up and Restoring the Cisco Configuration

Backing Up the Cisco Router Configuration

To copy the router’s configuration from a router to a TFTP server, you can use either the copy running-config tftp or the copy startup-config tftp command. Either one will back up the router configuration that’s currently running in DRAM or that’s stored in NVRAM.

Verifying the Current Configuration

To verify the configuration in DRAM, use the show running-config command (sh run ) like this:

Router#show running-config

Building configuration...

Current configuration : 776 bytes

version 12.4

The current configuration information indicates that the router is running version 12.4 of the IOS.

Verifying the Stored Configuration

Next, you should check the configuration stored in NVRAM. To see this, use the show startup-config command (sh start for short) like this:

Router#show startup-config

Using 776 out of 245752 bytes

version 12.4

Copying the Current Configuration to NVRAM

By copying running-config to NVRAM as a backup, as shown in the following output, you’re assured that your running-config will always be reloaded if the router gets rebooted:

Router#copy running-config startup-config

Destination filename [startup-config]?[enter]

Building configuration...

[OK]

Router#

Copying the Configuration to a TFTP Server

Once the file is copied to NVRAM, you can make a second backup to a TFTP server by using the copy running-config tftp command (copy run tftp for short), like this:

Router#copy running-config tftp

Address or name of remote host []?1.1.1.2

Destination filename [router-confg]?todd-confg

776 bytes copied in 0.800 secs (970 bytes/sec)

Router#

In the preceding example, I named the file todd-confg because I had not set a hostname for the router. If you have a hostname already configured, the command will automatically use the hostname plus the extension -confg as the name of the file.

Restoring the Cisco Router Configuration

If you want to restore the configuration to the version in the startup-config file use the copy startup-config running-config command (copy start run for short).

If you did copy the router’s configuration to a TFTP server as a second backup, you can restore the configuration using the copy tftp running-config command (copy tftp run for short) or the copy tftp startup-config command (copy tftp start for short), as shown here :

Router#copy tftp running-config

Address or name of remote host []?1.1.1.2

Source filename []?todd-confg

Destination filename[running-config]?[enter]

Accessing tftp://1.1.1.2/todd-confg...

Loading todd-confg from 1.1.1.2 (via FastEthernet0/0): !

[OK - 776 bytes]

776 bytes copied in 9.212 secs (84 bytes/sec)

Router#

Erasing the Configuration

To delete the startup-config file on a Cisco router, use the command erase startup-config, like this:

Router#erase startup-config

Erasing the nvram filesystem will remove all configuration files!

Continue? [confirm][enter]

[OK]

Erase of nvram: complete

Router#reload

System configuration has been modified. Save? [yes/no]:n

Proceed with reload? [confirm][enter]

*Mar 7 17:56:31.059: %SYS-5-RELOAD: Reload requested by console.

Reload Reason: Reload Command.

This command deletes the contents of NVRAM on the router. If you type reload at privileged mode and say no to saving changes, the router will reload and come up into setup mode.

Abstract of CCNA study guide-16 -Managing a Cisco Internetwork 1

2011-11-21T01:55:00.001-08:00

Managing a Cisco Internetwork

The Internal Components of a Cisco Router

Table below describes the major Cisco router components.

Cisco Router Components

Component	Description
Bootstrap	Stored in the microcode of the ROM. It will boot the router and then load the IOS.
POST (power-on self-test)	Stored in the microcode of the ROM, the POST is used to check the functionality of the router and which interfaces are present.
ROM monitor	Stored in the microcode of the ROM, used for manufacturing, testing, and troubleshooting.
Mini-IOS	Called the RXBOOT or bootloader by Cisco, it is a small IOS in ROM that can be used to bring up an interface and load a Cisco IOS into flash memory.
RAM	hold packet buffers, ARP cache and routing tables. Running-config is stored in RAM.
ROM	Used to start and maintain the router. Holds the POST , bootstrap and mini-IOS.
Flash memory	Stores the Cisco IOS by default.
NVRAM (nonvolatile RAM)	Used to hold the router and switch configuration. store The configuration register .
Configuration register	Used to control how the router boots up. This value can be found as the last line of the show version command output and by default is set to 0x2102, which tells the router to load the IOS from flash memory as well as to load the configuration from NVRAM.

The Router Boot Sequence

The Router boot sequence consists of the following steps:

1. The router performs a POST. The POST tests the hardware to verify that all components of the device are operational and present.

2. The bootstrap then looks for and loads the Cisco IOS software.default, the IOS software is loaded from flash memory in all Cisco routers.

3. The IOS software looks for a valid configuration file stored in NVRAM. This file is called startup-config

4. If a startup-config file is in NVRAM, the router will copy this file and place it in RAM and call the file running-config.

If a startup-config file is not in NVRAM, the router will broadcast out any interface that detects carrier detect (CD) for a TFTP host looking for a configuration, and when that fails , it will start the setup mode configuration process.

Managing Configuration Register

All Cisco routers have a 16-bit software register that’s written into NVRAM. By default, the configuration register is set to load the Cisco IOS from flash memory and to look for and load the startup-config file from NVRAM.

Understanding the Configuration Register Bits

The 16 bits (2 bytes) of the configuration register are read from 15 to 0, from left to right. The default configuration setting on Cisco routers is 0x2102. This means that bits 13, 8, and 1 are on, as shown in Table below . Notice that each set of 4 bits (called a nibble) is read in binary with a value of 8, 4, 2, 1.

Checking the Current Configuration Register Value

You can see the current value of the configuration register by using the show version command :

Router# sh version

Cisco IOS Software, 2800 Software (C2800NM-ADVSECURITYK9-M), Version

12.4(12), RELEASE SOFTWARE (fc1)

[output cut]

Configuration register is 0x2102

The last information is the value of the configuration register. The configuration register setting of 0x2102 tells the router to look in NVRAM for the boot sequence.

Changing the Configuration Register

These are the main reasons you would want to change the configuration register:

- To force the system into the ROM monitor mode

- To select a boot source and default boot filename

- To enable or disable the Break function

- To control broadcast addresses

- To set the console terminal baud rate

- To load operating software from ROM

- To enable booting from TFTP server

You can change the configuration register by using the config-register command.

The following commands tell the router to boot a small IOS from ROM:

Router(config)# config-register 0x2101

Router(config)#^Z

Router# sh ver

[output cut]

Configuration register is 0x2102 (will be 0x2101 at next reload)

Notice that the show version command displays the current configuration register value and also what that value will be when the router reboots. Any change to the configuration register won’t take effect until the router is reloaded. The 0x2101 will load the IOS from ROM the next time the router is rebooted.

Here is our router after setting the configuration register to 0x2101 and reloading:

Router(boot)#sh ver

[output cut]

ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)

Router uptime is 3 minutes

System returned to ROM by power-on

System image file is “flash:c2800nm-advsecurityk9-mz.124-12.bin”

[output cut]

Configuration register is 0x2101

At this point, if you typed show flash , you’d still see the IOS in flash memory ready to go. But we told our router to load from ROM, which is why the hostname shows up with (boot).

Router(boot)# sh flash

-#- --length-- -----date/time------ path

1 21710744 Jan 2 2007 22:41:14 +00:00 c2800nm-advsecurityk9-mz.124-12.bin

2 1823 Dec 5 2006 14:46:26 +00:00 sdmconfig-2811.cfg

3 4734464 Dec 5 2006 14:47:12 +00:00 sdm.tar

4 833024 Dec 5 2006 14:47:38 +00:00 es.tar

5 1052160 Dec 5 2006 14:48:10 +00:00 common.tar

6 1038 Dec 5 2006 14:48:32 +00:00 home.shtml

7 102400 Dec 5 2006 14:48:54 +00:00 home.tar

8 491213 Dec 5 2006 14:49:22 +00:00 128MB.sdf

9 1684577 Dec 5 2006 14:50:04 +00:00 securedesktop-ios-3.1.1.27-k9.pkg

10 398305 Dec 5 2006 14:50:34 +00:00 sslclient-win-1.1.0.154.pkg

32989184 bytes available (31027200 bytes used)

Recovering Passwords

If you’re locked out of a router because you forgot the password, you can change the configuration

register to recover it. The bit 6 in the configuration register is used to tell the router whether to use the contents of NVRAM to load a router configuration.

The default configuration register value is 0x2102, meaning that bit 6 is off. With the default setting, the router will look for and load a router configuration stored in NVRAM (startup-config).

To recover a password, you need to turn on bit 6. Doing this will tell the router to ignore the NVRAM contents. The configuration register value to turn on bit 6 is 0x2142.

Here are the main steps to password recovery:

1. Boot the router and interrupt the boot sequence (break), which will take into ROM monitor mode.

2. Change the configuration register to turn on bit 6 (with the value 0x2142).

3. Reload the router.

4. Enter privileged mode.

5. Copy the startup-config file to running-config.

6. Change the password.

7. Reset the configuration register to the default value.

8. Save the router configuration.

9. Reload the router (optional).

Interrupting the Router Boot Sequence

perform a break by pressing the Ctrl+Break key while the router first reboots. After you’ve performed a break, you should see some lines then the prompt:

rommon 1 >

At this point, you will be at the rommon 1> prompt, which is called ROM monitor mode.

Changing the Configuration Register

you can change the configuration register by using the config-register command. To turn on bit 6, use the configuration register value 0x2142.

Cisco ISR/2600 Series Commands

To change the bit value on a Cisco ISR/2600 series router, you just enter the command at the

rommon 1> prompt:

rommon 1 >confreg 0x2142

You must reset or power cycle for new config to take effect

rommon 2 >reset

Cisco 2500 Series Commands

To change the configuration register on a 2500 series router, type o after creating a break sequence on the router. This brings up a menu of configuration register option settings. To change the configuration register, enter the command o/r, followed by the new register value.

Configuration register = 0x2102 at last boot

Bit# Configuration register option settings:

15 Diagnostic mode disabled

14 IP broadcasts do not have network numbers

13 Boot default ROM software if network boot fails

12-11 Console speed is 9600 baud

10 IP broadcasts with ones

08 Break disabled

07 OEM disabled

06 Ignore configuration disabled

03-00 Boot file is cisco2-2500 (or ‘boot system’ command)

>o/r 0x2142

Reloading the Router and Entering Privileged Mode

At this point, you need to reset the router like this:

- From the ISR/2600 series router, type I (for initialize) or reset.

- From the 2500 series router, type I.

The router will reload and ask if you want to use setup mode. Answer no to entering setup mode, press Enter to go into user mode, and then type enable to go into privileged mode.

Viewing and Changing the Configuration

Copy the startup-config file to the running-config file:

copy startup-config running-config

Or use the shortcut:

copy start run

The configuration is now running in random access memory (RAM), and you’re in privileged mode, meaning that you can now view and change the configuration. But you can’t view the enable secret setting for the password since it is encrypted. To change the password, do this:

config t

enable secret todd

Resetting the Configuration Register and Reloading the Router

After you’re finished changing passwords, set the configuration register back to the default value with the config-register command:

config t

config-register 0x2102

Finally, save the new configuration with a copy running-config startup-config and reload the router.

Boot System Commands

You can configure router to boot another IOS if the flash is corrupted.

There are some boot commands you can play with that will help you manage the way your router boots the Cisco IOS—but remember, we’re talking about the router’s IOS here, not the router’s configuration!

Router>en

Router#config t

Router(config)#boot ?

bootstrap Bootstrap image file

config Configuration file

host Router-specific config file

network Network-wide config file

system System image file

the boot system command will allow you to tell the router which file to boot from flash memory. Remember that the router, by default, boots the first file found in flash. You can change that with the following commands:

Router(config)#boot system ?

WORD TFTP filename or URL

flash Boot from flash memory

ftp Boot from a server via ftp

mop Boot from a Decnet MOP server

rcp Boot from a server via rcp

rom Boot from rom

tftp Boot from a tftp server

Router(config)#boot system flash c2800nm-advsecurityk9-mz.124-12.bin

The next command makes your Router boot from a TFTP host:

Router(config)#boot system tftp ?

WORD System image filename

Router(config)#boot system tftp c2800nm-advsecurityk9-mz.124-12.bin ?

Hostname or A.B.C.D Address from which to download the file

Router(config)#boot system tftp c2800nm-advsecurityk9-mz.124-12.bin 1.1.1.2

Router(config)#

As your last recommended : if the IOS in flash doesn’t load and the TFTP host does not produce the IOS, load the mini-IOS from ROM like this:

Router(config)#boot system rom

Study/Book Resources for the CCNA 640-802, CCENT 640-822 & CCNA 640-816 exams

2011-11-20T00:20:00.001-08:00

CCNA : 640-822 ICND1 Interconnecting Cisco Networking Devices

CCNA : 640-816 ICND2 Interconnecting Cisco Networking Devices

CCNA:640-802 Cisco Certified Network Associate

Study/Book Resources for the CCNA 640-802, CCENT 640-822 & CCNA 640-816 exams

CCNA: Cisco Certified Network Associate Study Guide (640-802): Exam 640-802. (640-802)7th Edition edition (1 April 2011) with Dynamic Updates July-2011

Product Description

Learn from the Best – Cisco Networking Authority Todd LammleWritten by Cisco networking authority Todd Lammle, this comprehensive guide has been completely updated to reflect the latest CCNA 640–802 exam. Todd’s straightforward style provides lively examples, hands on and written labs, easy–to–understand analogies, and real–world scenarios that will not only help you prepare for the exam, but also give you a solid foundation as a Cisco networking professional.
This Study Guide teaches you how to

Describe how a network works
Configure, verify and troubleshoot a switch with VLANs and interswitch communications
Implement an IP addressing scheme and IP Services to meet network requirements in a medium–size Enterprise branch office network.
Configure, verify, and troubleshoot basic router operation and routing on Cisco devices
Explain and select the appropriate administrative tasks required for a WLAN
Identify security threats to a network and describe general methods to mitigate those threats
Implement, verify, and troubleshoot NAT and ACLs in a medium–size Enterprise branch office network.
Implement and verify WAN links

http://hotfile.com/dl/135607222/8b34ddc/Lammle_Todd_CCNA_7th_Edition.rar.html

Sybex - 640-802 CCNA Study Guide - 6th Edition August 2007(Todd Lammle)

Product Description

Completely Revised for the New 2007 Version of the CCNA Exam (#640-802) Cisco networking authority Todd Lammle has completely updated this new edition to cover all of the exam objectives for the latest version of the CCNA exam. Todd's straightforward style provides lively examples, easy-to-understand analogies, and real-world scenarios that will not only help you prepare for the exam, but also give you a solid foundation as a Cisco networking professional. Packed with updated topics that have been added to the 2007 version of the CCNA exam, this updated study guide features expanded coverage of key topic areas plus new material on switching, network address translation, and OSPF. Inside, find the complete instruction you need, including: *Full coverage of all exam objectives in a systematic approach, so you can be confident you're getting the instruction you need for the exam *Practical hands-on exercises and labs to reinforce critical skills, *Real-world scenarios that put what you've learned in the context of actual job roles *Challenging review questions in each chapter to prepare you for exam day *Exam Essentials, a key feature in each chapter that identifies critical areas you must become proficient in before taking the exam

http://hotfile.com/dl/135535355/8a84fa7/ccna-640-802-lammle-studyguide2007.rar.html

Sybex CCENT ICND1 Study Guide 640-822(Todd Lammle)

Product Description

Start your preparation for Cisco′s new CCENT entry–level networking certification, your entry point into Cisco′s popular CCNA certification track. This comprehensive study guide from leading Cisco authority Todd Lammle thoroughly prepares you for the Interconnecting Cisco Networking Devices, Part 1 exam (640–822) and the start of a career, with pages of exam essentials, real–world scenarios, and hands–on exercises. Topics include the operation of data networks, how to implement both switched and routed networks, and much more.

http://hotfile.com/dl/135539985/59ab26c/SYBEX_CCENTstudyGuide_640-822_By_Todd_Lammle.rar.html

Sybex - CCNA Fast Pass 3rd Edition Nov 2007(Todd Lammle)

Organized by exam objectives, this is a focused, concise review guide that works hand–in–hand with any learning tool, including the Sybex CCNA: Cisco Certified Network Associate Study Guide, 6th and Deluxe editions.

The book will consist of four high–level chapters, each mapping to the four main Domains of the exam skill–set. The book will drill down into the specifics of the exam, covering the following:

Designing Cisco internetworks
Developing an access list
Evaluating TCP/IP communication
Configuring routers and switches
Configuring IP addresses, subnet masks, and gateway addresses
Performing LAN, VLAN, and WAN troubleshooting
Understanding rules for packet control

http://hotfile.com/dl/135535397/fce6555/ccna-640-802-lammle-fastpass2007.rar.html

Sybex - Cliffs TestPrep - Cisco CCNA - April 2007(Todd Lammle)

Product Description

Written by test–prep specialists, this guide begins with a complete description of the exam, and then goes on to cover the four main areas that the test targets: planning and designing, implementation and operation, troubleshooting, and technology. The authors provide more than 500 practice questions with answers and explanations, share proven test–taking strategies, and offer ten full–length practice exams that are structured like the actual test so you’ll be familiar with the format.

http://hotfile.com/dl/135540429/719a4a1/ccna-640-802-lammle-cliffstestprep2007.rar.html

Sybex - 640-802 - Todd Lammle’s CCNA IOS Command Survival Guide 2008(Todd Lammle)

Product Description

Review

"Should be on every network administrator′s bookshelf." (Publishing News, Friday 19th October 2007)

Product Description

To become a Cisco Certified Network Associate (CCNA), you must learn the hundreds of IOS commands used by Cisco routers and switches. This handy reference from Cisco networking authority Todd Lammle is just what you need to master those commands. From a thorough introduction to Cisco′s basic operating system to making the transition to IPv6, Todd Lammle walks you through hundreds of commands with short, to–the–point explanations and plenty of figures and real–world examples.

http://hotfile.com/dl/135535344/094a8ea/ccna-640-802-lammle-iossurvivalguide2008.rar.html

Preplogic CCNA Mega Guide

Hidden Content

http://hotfile.com/dl/135539226/b4e9207/Preplogic_ccna_Mega_Guide.rar.htmll

CCNA Quick Reference Sheets (Cisco Press)

http://hotfile.com/dl/135535347/66e6390/ccna-640-802-quickreferencesheets2007.rar.html

Cisco Press - IP Addressing Fundamentals - October 2002(Mark A. Sportack)

Product Description

The reader-friendly explanation of how the IP address space works and how it is used

A reader-friendly introduction to the complex and confusing topic of IP addressing
Thorough and understandable explanations of the binary mathematics behind IP addressing
Complete coverage of the IPv4 address space without distractions of routing or transport protocols
Detailed explanations of subnetting and supernetting, Variable Length Subnet Masks (VLSMs), CIDR, NAT, portable address spaces, and IPv6
Strategies for managing an address space for enterprise WANs, data centers, and ISPs
Numerous examples and an easy-to-read style of writing that imparts a profound understanding of IP addressing

http://hotfile.com/dl/135539241/04ac96b/ccna-sportack-ipaddressingfundamentals2002.rar.html

Cisco Press - Cisco Networking Simplified - 2nd Edition December 2007(Jim Doherty)

Product Description

Cisco Networking Simplified
Second Edition

Master today’s world of Cisco networking with this book’s completely updated, fully illustrated visual approach
Easy enough for novices, substantive enough for networking professionals
Covers the latest networking topics—from network architecture to secure wireless, unified communications to telepresence

http://hotfile.com/dl/135539414/041759c/cisco-doherty-cisconetworkingsimplified2007.rar.html

Cisco Press - TCP-IP First-Step - December 2004(Mark A. Sportack)

Product Description

Your first step into the world of TCP/IP

No TCP/IP experience required
Includes clear and easily understood explanations
Makes learning easy

Your first step to understanding TCP/IP begins here!

Learn TCP/IP basics
Discover the power of TCP/IP components and subcomponents
Use hands-on activities to understand TCP/IP
Benefit from examples that illustrate the power of TCP/IP

Welcome to the world of TCP/IP!
TCP/IP is the world’s de facto communications protocol. It is the official protocol of the Internet and, consequently, has become the predominant communications protocol suite in many private networks and internetworks.

No TCP/IP experience needed!
TCP/IP First-Step explores TCP/IP concepts in a reader-friendly manner that assumes no previous experience. Learn about packetized data transfer, open networking, reference models, and standards bodies. Understand the architecture of the TCP/IP protocol suite and learn about its components, functions, and respective uses. TCP/IP First-Step helps you understand TCP/IP’s role in the network.

http://hotfile.com/dl/135539251/4388cc8/ccna-tcpip-first-step2004.rar.html

Cisco Press - Cisco IP Routing Fundamentals - Mark Sportack 1999

Product Description

A comprehensive ntroduction to routing concepts and protocols in IP networks.

Comprehensive review of the operational mechanics of today's leading routing protocols, including IGRP, EIGRP, OSPF, RIP, and RIP-2
Detailed explanation of IP addressing, including classful and classless addresses, subnetting, supernetting, Classless Interdomain Routing (CIDR), and Variable Length Subnet Masks (VLSM)
Side-by-side comparisons of various LAN segmentation technologies, including bridges, switches, and routers
Exploration of how routers are used to build wide area networks
Examination of the future of routing, including IPv6, next generation routing protocols, host-based routing, and IP Switching

IP Routing Fundamentals is the definitive introduction to routing in IP networks. This comprehensive guide explores the mechanics of routers, routing protocols, network interfaces, and operating systems.
This reference provides essential background information for network professionals who are deploying and maintaining LANs and WANs, as well as IT managers who are seeking information on how evolving internetworking technology will affect future networks. Part I discusses the many roles routers play in networks, Part II talks about the inner working of routers, Part III works with the operational issues of routing protocols, and Part IV addresses implementation issues that provide practical insight, in addition to a discussion of the future of routing.

http://hotfile.com/dl/135538763/26b7d30/ccna-routingfundamentals1999.rar.html

Cisco Press - Routing First-Step - September 2004(Bill Parkhurst)

Product Description

Your first step into the world of routing

No routing experience required
Includes clear and easily understood explanations
Makes learning easy

Your first step to understanding routing begins here!

Learn routing basics simply and easily
Explore how network traffic gets from here to there
Understand routing tools and technologies
Reinforce your understanding with chapter review questions

Welcome to the world of routing!

Routing is the technology that enables worldwide Internet communication. Many people involved with networking technologies or companies need to know how routing works. But learning about routing tends to involve a complex web of terms and acronyms-a language that can be difficult and unfamiliar.

No routing experience needed!

Routing First-Step explains the basics of Internet routing in language all of us can understand. This book takes you on a guided tour of routing, starting with systems you are familiar with: the postal system, the telephone system, and the interstate highway system. From there, you'll learn routing simply and easily. Whether you are looking to take your first step into a career in networking or are interested only in gaining knowledge of the technology, this book is for you!

http://hotfile.com/dl/135538765/076a130/ccna-routing-first-step2004.rar.html

Cisco Press - LAN Switching First-Step - July 2004(Matthew J. Castelli)

Product Description

Your first step into the world of LAN switching

No LAN switching experience required
Includes clear and easily understood explanations
Makes learning easy

Your first step to LAN switching begins here!

Learn local-area network (LAN) key concepts and terminology
Identify key issues involved with designing and managing a switched LAN
Answer the question: do I need a hub, a bridge, or a switch?

Welcome to the world of LAN switching!
Network switches work by connecting network paths together and making intelligent decisions about moving traffic in a network. By keeping track of changes in the network, switches reduce congestion and improve speed.
No LAN switching experience needed!
LAN Switching First-Step explains the basics of LAN switching in easy-to-grasp language that all of us can understand. This book takes you on a guided tour of the key concepts behind how bridges and switches work. Whether you are looking to take your first step into a career in networking or are interested in just gaining a conversational knowledge of the technology, this book is for you!

http://hotfile.com/dl/135601282/967299a/ccna-switching-first-step2004.rar.html

Cisco Press - 640-802 CCNA Portable Command Guide - 2nd Edition July 2007(Scott Empson)

Product Description

CCNA Portable Command Guide
Second Edition
All the CCNA 640-802 commands in one compact, portable resource
Preparing for the CCNA® exam? Here are all the CCNA-level commands you need in one condensed, portable resource. The CCNA Portable Command Guide, Second Edition, is filled with valuable, easy-to-access information and is portable enough for use whether you’re in the server room or the equipment closet.

This book has been completely updated to cover topics in the ICND1 640-822, ICND2 640-816, and CCNA 640-802 exams. Use this quick reference resource to help you memorize commands and concepts as you work to pass the CCNA exam. The guide summarizes all CCNA certification-level Cisco IOS® Software commands, keywords, command arguments, and associated prompts, providing you with tips and examples of how to apply the commands to real-world scenarios. Configuration examples throughout the book provide you with a better understanding of how these commands are used in simple network designs.

http://hotfile.com/dl/135535341/6e1422a/ccna-640-802-empson-commandguide2007.rar.html

Cisco Press - 640-822 CCENT,CCNA,ICND1 Official Exam Certification Guide - 2nd Edition August 2007(Wendell Odom)

Product Description

The official study guide helps you master all the topics on the CCENT and CCNA ICND1 exam, including

TCP/IP and OSI networking models
Operating Cisco routers and LAN switches
Ethernet switch configuration and troubleshooting

Wireless LANs
IP addressing and subnetting
Routing protocols
Router configuration and troubleshooting
Network Security
WAN concepts and configuration

http://hotfile.com/dl/135601954/c3ea187/ccna-640-802-odom-examcertguide01-2007.rar.html

Book Only

Cisco Press - 640-816 & 640-802 CCNA,ICND2 Official Exam Certification Guide - 2nd Edition August 2007(Wendell Odom)

The official study guide helps you master all the topics on the CCNA ICND2 exam, including

Virtual LANs and Spanning Tree Protocol
Static and connected routes
VLSM and route summarization
IP access control lists
OSPF and EIGRP configuration
Point-to-point WANs
Frame Relay
VPNs
Network address translation
IPv6
Troubleshooting

http://hotfile.com/dl/135601953/1fa16b6/ccna-640-802-odom-examcertguide02-2007.rar.html

Book Only

Cisco Press - 640-822 CCENT,CCNA,ICND1 Official Exam Certification Guide - 2nd Edition August 2007(Wendell Odom)
2 CD's http://www.ciscopress.com/bookstore/product.asp?isbn=1587201828
Use Flv Player http://www.flvsoft.com/flv_player/ to play the FLV files on CD 2
Read the included readme.txt for information about what to do with the ISO (CD Image) Files

http://hotfile.com/dl/135538817/9def9e8/ccna-ccent-640-822-odom-icnd1examcertguide-2007CD.rar.html

Cisco Press - 640-816 & 640-802 CCNA,ICND2 Official Exam Certification Guide - 2nd Edition August 2007(Wendell Odom)
2 CD's http://www.ciscopress.com/bookstore/product.asp?isbn=158720181X
Use Flv Player http://www.flvsoft.com/flv_player/ to play the FLV files on CD 2
Read the included readme.txt for information about what to do with the ISO (CD Image) Files

http://hotfile.com/dl/135539292/93f0a02/ccna-640-816_640-802-odom-icnd2examcertguide-2007CD.rar.html

Abstract of CCNA study guide-15 -Cisco IOS Basic configurations 4

2011-11-18T09:24:00.001-08:00

Continue the series of Abstract CCNA study guide book .

Viewing, Saving, and Erasing Configurations

You can manually save the file from DRAM to NVRAM by using the copy running-config startup-config command (you can use the shortcut copy run start also):

Todd#copy running-config startup-config

Destination filename [startup-config]? [press enter]

Building configuration...

When you see a question with an answer in [], it means that if you just press Enter, you’re choosing the default answer.

Also, when the command asked for the destination filename, the default answer was startup-config.

You can view the files by typing show running-config or show startup-config from privileged mode. The sh run command, which is a shortcut for show running-config, tells us that we are viewing the current configuration:

Todd#show running-config

Building configuration...

Current configuration : 3343 bytes

version 12.4

[output cut]

The sh start command shows us the configuration that will be used the next time the router is reloaded. It also tells us how much NVRAM is being used to store the startup-config file. Here’s an example:

Todd#show startup-config

Using 1978 out of 245752 bytes

version 12.4

[output cut]

Deleting the Configuration and Reloading the Router

You can delete the startup-config file by using the erase startup-config command:

Todd#erase startup-config

Erasing the nvram filesystem will remove all configuration files! Continue? [confirm][enter]

[OK]

Erase of nvram: complete

Todd#

*Feb 28 23:51:21.179: %SYS-7-NV_BLOCK_INIT: Initialized the geometry of nvram

Todd#sh startup-config

startup-config is not present

Todd#reload

Proceed with reload? [confirm]System configuration has been modified. Save? [yes/no]: n

If you reload or power down and up the router after using the erase startup-config command, you’ll be offered setup mode because there’s no configuration saved in NVRAM.

You can press Ctrl+C to exit setup mode at any time (the reload command can only be used from privileged mode).

Verifying Your Configuration

show running-config would be the best way to verify your configuration and show startup-config would be the best way to verify the configuration that’ll be used the next time the router is reloaded.

you can verify your configuration with utilities such as Ping , Traceroute and Telnet.

Telnet, FTP, and HTTP are really the best tools because they use IP at the Network layer and TCP at the Transport layer to create a session with a remote host.

Router#telnet ?

WORD IP address or hostname of a remote system

From the router prompt, you just type a hostname or IP address and it will assume you want to telnet—you don’t need to type the actual command, telnet.

Verifying with the show interface Command

The show interfaces command displays the configurable parameters and statistics of all interfaces on a router.

This command is very useful for verifying and troubleshooting router and network issues.

The following output is from my freshly erased and rebooted 2811 router:

Router#sh int f0/0

FastEthernet0/0 is up, line protocol is up

Hardware is MV96340 Ethernet, address is 001a.2f55.c9e8 (bia 001a.2f55.c9e8)

Internet address is 192.168.1.33/27

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

[output cut]

Router#

first, I’ve got to ask you, What subnet is the FastEthernet 0/0 a member of and what’s the broadcast address and valid host range? Easy 192.168.1.33/27

The show interfaces command will show you if you are receiving errors on the interface, and it will show you the maximum transmission units (MTUs), bandwidth (BW), reliability (255/255 means perfect!), and load (1/255 means no load).

Have another look to the sh int command

Router#sh int fa0/0

FastEthernet0/0 is up, line protocol is up

The first parameter refers to the Physical layer, and it’s up when it receives carrier detect. The second parameter refers to the Data Link layer, and it looks for keepalives from the connecting end. (Keepalives are used between devices to make sure connectivity has not dropped.)

Here’s an example of where the problem usually is found—on serial interfaces:

Router#sh int s0/0/0

Serial0/0 is up, line protocol is down

If you see that the line is up but the protocol is down, as shown above, you’re experiencing a clocking (keepalive) or framing problem—possibly an encapsulation mismatch. Check the keepalives on both ends to make sure that they match; that the clock rate is set, if needed, and that the encapsulation type is the same on both ends. The output above would be considered a Data Link layer problem.

If you discover that both the line interface and the protocol are down, it’s a cable or interface problem.

The following output would be considered a Physical layer problem:

Router#sh int s0/0/0

Serial0/0 is down, line protocol is down

If one end is administratively shut down:

Router#sh int s0/0/0

Serial0/0 is administratively down, line protocol is down

To enable the interface, use the command no shutdown from interface configuration mode.

Another important configuration to notice is the keepalive, which is 10 seconds by default. Each router sends a keepalive message to its neighbor every 10 seconds, and if both routers aren’t configured for the same keepalive time, it won’t work.

Router#sh int s0/0/0

Serial0/0 is up, line protocol is up

Hardware is HD64570

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation HDLC, loopback not set, keepalive set (10 sec)

You can clear the counters on the interface by typing the command clear counters:

Router#clear counters s0/0/0

Verifying with the show ip interface Command

The show ip interface command will provide you with information regarding the layer 3 configurations of a router’s interfaces:

Router#sh ip interface

FastEthernet0/0 is up, line protocol is up

Internet address is 1.1.1.1/24

Broadcast address is 255.255.255.255

Address determined by setup command

MTU is 1500 bytes

Helper address is not set

Directed broadcast forwarding is disabled

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is enabled

Security level is default

Split horizon is enabled

[output cut]

The status of the interface, the IP address and mask, information on whether an access list is set on the interface, and basic IP information are included in this output.

Using the show ip interface brief Command

The show ip interface brief command is probably one of the most helpful commands that you can ever use on a Cisco router. This command provides a quick overview of the router’s interfaces, including the logical address and status:

Router#sh ip int brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 unassigned YES unset up up

FastEthernet0/1 unassigned YES unset up up

Serial0/0/0 unassigned YES unset up down

Serial0/0/1 unassigned YES unset administratively down down

Serial0/1/0 unassigned YES unset administratively down down

Serial0/2/0 unassigned YES unset administratively down down

Remember, administratively down means that you need to type no shutdown under the

interface. Notice that Serial0/0/0 is up/down, which means that the physical layer is good and

carrier detect is sensed but no keepalives are being received from the remote end. In a nonproduction

network, like the one I am working with, the clock rate isn’t set.

Verifying with the show protocols Command

The show protocols command used to see the status of layers 1 and 2 of and IP addresses of each interface:

Router#sh protocols

Global values:

Internet Protocol routing is enabled

Ethernet0/0 is administratively down, line protocol is down

Serial0/0 is up, line protocol is up

Internet address is 100.30.31.5/24

Serial0/1 is administratively down, line protocol is down

Serial0/2 is up, line protocol is up

Internet address is 100.50.31.2/24

Loopback0 is up, line protocol is up

Internet address is 100.20.31.1/24

Using the show controllers Command

The show controllers command displays information about the physical interface itself.

It’ll also give you the type of serial cable plugged into a serial port. Usually, this will only be a DTE cable that plugs into a type of data service unit (DSU).

Router#sh controllers serial 0/0

HD unit 0, idb = 0x1229E4, driver structure at 0x127E70

buffer size 1524 HD unit 0, V.35 DTE cable

cpb = 0xE2, eda = 0x4140, cda = 0x4000

Abstract of CCNA study guide-14 -Cisco IOS Basic configurations 3

2011-11-18T09:13:00.001-08:00

Continue the series of Abstract CCNA study guide book .

Router Interfaces

Different routers use different methods to choose the interfaces used on them. For instance, the following command shows a Cisco 2522 router with 10 serial interfaces, labeled 0 through 9:

Router(config)#int serial ?

<0-9> Serial interface number

Then we can choose serial port 5, for example:

Router(config)#int serial 5

Router(config)-if)#

The 2522 router has one Ethernet 10BaseT port, and typing interface ethernet 0 can configure that interface, as seen here:

Router(config)#int ethernet ?

<0-0> Ethernet interface number

Router(config)#int ethernet 0

Router(config-if)#

As I showed you above, the 2500 router is a fixed-configuration router. This means that when you buy that model, you’re stuck with that physical configuration.

To configure an interface, we used the interface type number sequence, but with the 2600 and 2800 series routers (actually, any ISR router for that matter), there’s a physical slot in the router, with a port number on the module plugged into that slot. So on a modular router, the configuration would be interface type slot/port, as seen here:

Router(config)#int fastethernet ?

<0-1> FastEthernet interface number

Router(config)#int fastethernet 0

% Incomplete command.

Router(config)#int fastethernet 0?

Router(config)#int fastethernet 0/?

<0-1> FastEthernet interface number

For the ISR series, it’s basically the same, only you get even more options. For example, the built-in FastEthernet interfaces work with the same configuration we used with the 2600 series:

Todd(config)#int fastEthernet 0/?

<0-1> FastEthernet interface number

Todd(config)#int fastEthernet 0/0

Todd(config-if)#

But the rest of the modules are different—they use three numbers instead of two. The first 0 is the router itself, and then you choose the slot, and then the port. Here’s an example of a serial interface on my 2811:

Todd(config)#interface serial ?

<0-2> Serial interface number

Todd(config)#interface serial 0/0/?

<0-1> Serial interface number

Todd(config)#interface serial 0/0/0

Todd(config-if)#

you should always view a running-config output first so you know what interfaces you have to deal with.

Just understand that if you type interface e0 on a 2500, interface fastethernet 0/0 on a 2600, or interface serial 0/1/0 on a 2800, all you’re doing is choosing an interface to configure, and basically, they’re all configured the same way after that.

Bringing Up an Interface

You can disable an interface with the command shutdown and enable it with the no shutdown command.

If an interface is shut down, it’ll display administratively down when you use the show interfaces command (sh int for short) or show running-config :

Todd#sh int f0/1

FastEthernet0/1 is administratively down, line protocol is down

[output cut]

All interfaces are shut down by default.

You can bring up the interface with the no shutdown command (no shut for short):

Todd#config t

Todd(config)#int f0/1

Todd(config-if)#no shutdown

Configuring an IP Address on an Interface

To configure IP addresses on an interface, use the ip address command from interface configuration mode:

Todd(config)#int f0/1

Todd(config-if)#ip address 172.16.10.2 255.255.255.0

Don’t forget to enable the interface with the no shutdown command.

If you want to add a second subnet address to an interface, you have to use the secondary parameter. If you type another IP address and press Enter, it will replace the existing IP address and mask.

So let’s try it. To add a secondary IP address, just use the secondary parameter:

Todd(config-if)#ip address 172.16.20.2 255.255.255.0 ?

secondary Make this IP address a secondary address

Todd(config-if)#ip address 172.16.20.2 255.255.255.0 secondary

I really wouldn’t recommend having multiple IP addresses on an interface because it’s ugly and inefficient.

Using the Pipe

The pipe is used as output modifier .This pipe ( | ) allows us to wade through all the configurations or other long outputs and get straight to our goods fast. Here’s an example:

Todd#sh run | ?

append Append redirected output to URL (URLs supporting append operation only)

begin Begin with the line that matches

exclude Exclude lines that match

include Include lines that match

redirect Redirect output to URL

section Filter a section of output

tee Copy output to URL

Todd#sh run | begin interface

interface FastEthernet0/0

description Sales VLAN

ip address 10.10.10.1 255.255.255.248

interface FastEthernet0/1

ip address 172.16.20.2 255.255.255.0 secondary

ip address 172.16.10.2 255.255.255.0

I use it a lot when I am looking at a large routing table to find out whether a certain route is in the

routing table. Here’s an example:

Todd#sh ip route | include 192.168.3.32

R 192.168.3.32 [120/2] via 10.10.10.8, 00:00:25, FastEthernet0/0

Todd#

Serial Interface Commands

Before you configure a serial interface, you need some key information— like knowing that the interface will usually be attached to a CSU/DSU type of device that provides clocking for the line to the router, as I’ve shown in Figure below.

DTE Here you can see that the serial interface is used to connect to a DCE network via a CSU/DSU that provides the clocking to the router interface. But if you have a back-to-back configuration (for example, one that’s used in a lab environment like I’ve shown you in Figure 4.5), one end— the data communication equipment (DCE) end of the cable—must provide clocking!

By default, Cisco routers are all data terminal equipment (DTE) devices, which means that you must configure an interface to provide clocking if you need it to act like a DCE device.

You configure a DCE serial interface with the clock rate command:

Todd#config t

Todd(config)#int s0/0/0

Todd(config-if)#clock rate 1000000

The clock rate command is set in bits per second. Besides looking at the cable end to check for a label of DCE or DTE, you can see if a router’s serial interface has a DCE cable connected with the show controllers int command:

Todd#sh controllers s0/0/0

Interface Serial0/0/0

Hardware is GT96K

DTE V.35idb at 0x4342FCB0, driver data structure at 0x434373D4

Here is an example of an output that shows a DCE connection:

Todd#sh controllers s0/2/0

Interface Serial0/2/0

Hardware is GT96K

DCE V.35, clock rate 1000000

The next command you need to get acquainted with is the bandwidth command.

Here’s an example of using the bandwidth command:

Todd#config t

Todd(config)#int s0/0/0

Todd(config-if)#bandwidth ?

<1-10000000> Bandwidth in kilobits

inherit Specify that bandwidth is inherited

receive Specify receive-side bandwidth

Todd(config-if)#bandwidth 1000

Did you notice that, the bandwidth command is configured in kilobits?

Abstract of CCNA study guide-13 -Cisco IOS Basic configurations 2

2011-11-18T09:09:00.001-08:00

Continue the series of Abstract CCNA study guide book .
Router and Switch Administrative Configurations

The administrative functions that you can configure on a router and switch are as follows:

-Hostnames

-Banners

-Passwords

-Interface descriptions

Hostnames

You can set the identity of the router with the hostname command.

yourname#config t

yourname(config)#hostname Todd

Todd(config)#hostname Atlanta

Atlanta(config)#hostname Todd

Banners

A banner is more than just a little cool—one very good reason for having a banner is to give any and all who dare attempt to telnet or dial into your internetwork a little security notice.

Make sure you’re familiar with these four available banner types: exec process creation banner, incoming terminal line banner, login banner, and message of the day banner:

Todd(config)#banner ?

LINE c banner-text c, where ‘c’ is a delimiting character

exec Set EXEC process creation banner

incoming Set incoming terminal line banner

motd Set Message of the Day banner

prompt-timeout Set Message for login authentication timeout

slip-ppp Set Message for SLIP/PPP

Message of the day (MOTD) is the most extensively used banner. It gives a message to every person dialing into or connecting to the router via Telnet or an auxiliary port, or a console port as seen here:

Todd(config)#banner motd #

Enter TEXT message. End with the character ‘#’.

$ Acme.com network, then you must disconnect immediately.

Todd(config)#^Z

You can use any character you want for it, but (I hope this is obvious) you can’t use the delimiting character in the message it self .Also, once the message is complete, press Enter, then the delimiting character, and then Enter again.

Setting Passwords

Five passwords are used to secure your Cisco routers: console, auxiliary, telnet (VTY), enable password, and enable secret.

The enable secret and enable password are used to set the password that’s used to secure privileged mode. This will prompt a user for a password when the enable command is used.

The other three are used to configure a password when user mode is accessed through the console port, the auxiliary port, or Telnet.

Enable Passwords

You set the enable passwords from global configuration mode like this:

Todd(config)#enable ?

last-resort Define enable action if no TACACS servers respond

password Assign the privileged level password

secret Assign the privileged level secret

use-tacacs Use TACACS to check enable passwords

The following points describe the enable password parameters:

last-resort Allows you to still enter the router if you set up authentication through a TACACS server and it’s not available. But it isn’t used if the TACACS server is working.

password Sets the enable password on older, pre-10.3 systems, and isn’t ever used if an enable secret is set.

secret This is the newer, encrypted password that overrides the enable password if it’s set.

use-tacacs This tells the router to authenticate through a TACACS server.

Todd(config)#enable secret todd

Todd(config)#enable password todd

The enable password you have chosen is the same as your enable secret. This is not recommended. Re-enter the

enable password.

If you try to set the enable secret and enable passwords the same, the router will give you warning to change the second password.

User-mode passwords are assigned by using the line command:

Todd(config)#line ?

<0-337> First Line number

aux Auxiliary line

console Primary terminal line

tty Terminal controller

vty Virtual terminal

x/y Slot/Port for Modems

x/y/z Slot/Subslot/Port for Modems

Here are the lines to be concerned with:

aux Sets the user-mode password for the auxiliary port.

console Sets a console user-mode password.

vty Sets a Telnet password on the router. If this password isn’t set, then Telnet can’t be used by default.

To configure the user-mode passwords, you configure the line you want and use either the login or no login command to tell the router to prompt for authentication. The next sections will provide a line-by-line example of the configuration of each line configuration

Auxiliary Password

Todd#config t

Todd(config)#line aux ?

<0-0> First Line number

Todd(config)#line aux 0

Todd(config-line)#password aux

Todd(config-line)#login

It’s important to remember the login command or the auxiliary port won’t prompt for authentication.

Console Password

Todd(config)#line console ?

<0-0> First Line number

Todd(config-line)#password console

Todd(config-line)#login

There are a few other important commands to know for the console port.

For one, the exec-timeout 0 0 command sets the time-out for the console EXEC session to zero, which basically means to never time out. The default time-out is 10 minutes. (If you’re feeling mischievous, try this on people at work: Set it to 0 1. That will make the console time out in 1 second! And to fix it, you have to continually press the down arrow key while changing the time-out time with your free hand!)

logging synchronous is a very cool command, and it should be a default command, but it’s not. It stops annoying console messages from popping up and disrupting the input you’re trying to type.

Here’s an example of how to configure both commands:

Todd(config-line)#line con 0

Todd(config-line)#exec-timeout ?

<0-35791> Timeout in minutes

Todd(config-line)#exec-timeout 0 ?

<0-2147483> Timeout in seconds

Todd(config-line)#exec-timeout 0 0

Todd(config-line)#logging synchronous

Telnet Password

To set the user-mode password for Telnet access into the router, use the line vty command.

Routers that aren’t running the Enterprise edition of the Cisco IOS default to five VTY lines, 0 through 4. But if you have the Enterprise edition, you’ll have significantly more. The best way to find out how many lines you have is to use that question mark:

Todd(config-line)#line vty 0 ?

% Unrecognized command

Todd(config-line)#exit

Todd(config)#line vty 0 ?

<1-1180> Last Line number

Todd(config)#line vty 0 1180

Todd(config-line)#password telnet

Todd(config-line)#login

Remember, you cannot get help from your (config-line)# prompt. You must go back to privilege mode in order to use the question mark (?).

you can allow Telnet connections without a password by using the no login command:

SFRouter(config-line)#line vty 0 4

SFRouter(config-line)#no login

Setting Up Secure Shell (SSH)

Instead of Telnet, you can use Secure Shell, which creates a more secure session than the Telnet application that uses an unencrypted data stream. Secure Shell (SSH) uses encrypted keys to send data so that your username and password are not sent in the clear.

Here are the steps to setting up SSH:

1. Set your hostname:

Router(config)#hostname Todd

2. Set the domain name:

Todd(config)#ip domain-name Lammle.com

3. Generate the encryption keys for securing the session:

Todd(config)#crypto key generate rsa general-keys modulus ?

<360-2048> size of the key modulus [360-2048]

Todd(config)#crypto key generate rsa general-keys modulus 1024

The name for the keys will be: Todd.Lammle.com

% The key modulus size is 1024 bits

4. Set the max idle timer for a SSH session:

Todd(config)#ip ssh time-out ?

<1-120> SSH time-out interval (secs)

Todd(config)#ip ssh time-out 60

5. Set the max failed attempts for an SSH connection:

Todd(config)#ip ssh authentication-retries ?

<0-5> Number of authentication retries

Todd(config)#ip ssh authentication-retries 2

6. Connect to the vty lines of the router:

Todd(config)#line vty 0 1180

7. Last, configure SSH and then Telnet as access protocols:

Todd(config-line)#transport input ssh telnet

If you do not use the keyword telnet at the end of the command string, then only SSH will work on the router. understand that SSH is more secure than Telnet.

Encrypting Your Passwords

Because only the enable secret password is encrypted by default, you’ll need to manually configure the user-mode and enable passwords for encryption.

you can see all the passwords except the enable secret when performing a show running-config on a router:

Todd#sh running-config

To manually encrypt your passwords, use the service password-encryption command.

Here’s an example of how to do it:

Todd#config t

Enter configuration commands, one per line. End with CNTL/Z.

Todd(config)#service password-encryption

Todd(config)#exit

Todd#sh run

Building configuration...

[output cut]

Todd#config t

Todd(config)#no service password-encryption

Todd(config)#^Z

Todd#

There you have it! The passwords will now be encrypted. You just encrypt the passwords, perform a show run, and then turn off the command. You can see that the enable password and the line passwords are all encrypted.

if you set your passwords and then turn on the service password-encryption command, you have to perform a show running-config before you turn off the encryption service or your passwords won’t be encrypted. You don’t have to turn off the encryption service at all; you’d only do that if your router is running low on processes.

And if you turn on the service before you set your passwords, then you don’t even have to view them to get them encrypted.

Descriptions

The description command is a helpful because you can, for instance, use it to keep track of circuit numbers.

Todd#config t

Todd(config)#int s0/0/0

Todd(config-if)#description Wan to SF circuit number 6fdda12345678

Todd(config-if)#int fa0/0

Todd(config-if)#description Sales VLAN

Todd(config-if)#^Z

Todd#

You can view the description of an interface with either the show running-config command or the show interface command:

Todd#sh run

[output cut]

interface FastEthernet0/0

description Sales VLAN

ip address 10.10.10.1 255.255.255.248

[output cut]

Todd#sh int f0/0

FastEthernet0/0 is up, line protocol is down

Hardware is MV96340 Ethernet, address is 001a.2f55.c9e8 (bia 001a.2f55.c9e8)

Description: Sales VLAN

Doing the do Command

Beginning with IOS version 12.3, Cisco has finally added a command to the IOS that allows you to view the configuration and statistics from configuration mode.

Todd(config)#do show run

Building configuration...

Current configuration : 3276 bytes

[output cut]

Todd(config)#do sh int f0/0

FastEthernet0/0 is up, line protocol is down

Abstract of CCNA study guide-12 -Cisco IOS Basic configurations 1

2011-11-18T08:58:00.001-08:00

Continue the series of Abstract CCNA study guide book .
The IOS User Interface

The Cisco Internetwork Operating System (IOS) is the kernel of Cisco routers and most switches.

Cisco Router IOS

These are some important things that the Cisco router IOS software is responsible for:

- Carrying network protocols and functions

- Connecting high-speed traffic between devices

- Adding security to control access and stop unauthorized network use

- Providing scalability for ease of network growth and redundancy

- Supplying network reliability for connecting to network resources

Connecting to a Cisco Router

There are different ways to Connect to Router:

the first is the console port. The Console port is usually an RJ-45 (8-pin modular) connection located at the back of the router—by default, there’s May or may not be a password set. The new ISR routers use cisco as the username and cisco as the password by default.

The second is an auxiliary port which is really the same thing as a console port. But an auxiliary port also allows you to configure modem commands so that a modem can be connected to the router.

It lets you dial up a remote router and attach to the auxiliary port if the router is down and you need to configure it out-of-band (meaning out of the network).

The third is Telnet, You can use Telnet to connect to any active interface on a router, such as an Ethernet or serial port.

Next Figure shows an illustration of a Cisco 2600 series modular router

The 2600 series router can have multiple serial interfaces, which can be used for connecting a T1 or Frame Relay using a serial V.35 WAN connection. Multiple Ethernet or FastEthernet ports can be used on the router, depending on the model. This router also has one console and one auxiliary connection via RJ-45 connectors.

Another router I want to talk about is the 2800 series . This router has replaced the 2600 series router series and is referred to as Integrated Services Router (ISR), because many of the services, like security, are built into it. It’s a modular device like the 2600, but it’s much faster.

The 2800 has the Security Device Manager (SDM) preinstalled. The SDM is a Web-based device-management tool for Cisco routers that can help you configure a router via a web console.

Bringing Up a Router

When you first bring up a Cisco router,

1- run a power-on self-test (POST).

2- load the Cisco IOS from flash memory

3- the IOS loads the startup-config that’s stored in NVRAM.

4- The startup-config will be copied from NVRAM into RAM And called running-config.

if there isn’t a configuration in NVRAM, the router will broadcast looking for a valid one on a TFTP host. If the broadcast fails, it will then go into what is called setup mode —a step-by-step process to help you configure the router.

You can also enter setup mode at any time from the command line by typing the command setup

from privileged mode.

Command-Line Interface (CLI)

To use the CLI, press Enter after the router finishes booting up. After you do that, the router will respond with messages that tell you all about the status of each and every one of its interfaces and then display a banner and ask you to log in.

Entering the CLI from a Non-ISR Router

After the interface status messages appear and you press Enter, the Router> prompt will appear. This is called user exec mode (user mode), and it’s mostly used to view statistics, but it’s also a stepping stone to logging in to privileged mode.

You can only view and change the configuration of a Cisco router in privileged exec mode (privileged mode), which you can enter with the enable command.

Here’s how:

Router>enable

Router#

You now end up with a Router# prompt, which indicates that you’re in privileged mode, where you can You can go back from privileged mode into user mode by using the disable command:

Router#disable

Router>

At this point, you can type logout from either mode to exit the console:

Router>logout

Router con0 is now available

Press RETURN to get started.

Overview of Router Modes

global configuration mode: you can enter global configuration mode by typing configure terminal (or config t for short) in which you can make global changes to the router and changes the running-config.

A global command (a command run from global config) is set only once and affects the entire router.

To change the startup-config—the configuration stored in NVRAM—you use the configure memory command (or config mem for short), which merges the startup-config file into the running-config file in RAM.

If you want to change a router configuration stored on a TFTP host you use the configure network command (or config net for short), which also merges the file with the running-config file in RAM.

CLI Prompts

It’s really important that you understand the different prompts you can find when configuring a

router.

Editing and Help Features

You can use the Cisco advanced editing features to help you configure your router. If you type in a question mark (?) at any prompt, you’ll be given a list of all the commands available from that prompt:

By typing the clock ? command, you’ll get a list of the next possible parameters and what they do. Notice that you should just keep typing a command, a space, and then a question mark until (carriage return) is your only option.

If you’re typing commands and receive

yourname#clock set 11:15:11

% Incomplete command.

Means the command isn’t done yet. Just press the up arrow key to redisplay the last command entered, and then continue with the command by using your question mark.

And if you receive the error

yourname(config)#access-list 110 permit host 1.1.1.1

% Invalid input detected at ‘^’ marker.

Means you’ve entered a command incorrectly. See that little caret—the ^? It’s a very helpful tool that

marks the exact point where you blew it and entered the command incorrectly.

Here’s another example of when you’ll see the caret:

yourname#sh serial 0/0/0

% Invalid input detected at ‘^’ marker.

The problem is that the full command is show interface serial 0/0/0.

Now if you receive the error

yourname#sh ru

% Ambiguous command: “sh ru”

means there are multiple commands that begin with the string you entered . Use the question mark to find the command you need:

yourname#sh ru?

rudpv1 running-config

Table 4.2 lists the enhanced editing commands available on a Cisco router.

Next TABLE Enhanced Editing Commands

You can review the router-command history with the commands shown in Table below.

The following example demonstrates the show history command and how to change the history size, as well as how to verify it with the show terminal command. First, use the show history command to see the last 20 commands that were entered on the router:

yourname#show history

Now use the show terminal command to verify the terminal history size:

yourname#show terminal

[output cut]

Editing is enabled.

History is enabled, history size is 20.

[output cut]

The terminal history size command, used from privileged mode, can change the size of the history buffer:

yourname#terminal history size ?

<0-256> Size of history buffer

yourname#terminal history size 25

You verify the change with the show terminal command:

Gathering Basic Routing Information

The show version command will provide basic configuration for the system hardware and the software version and the boot images. Here’s an example:

yourname#show version

what is CCNA

2011-11-16T12:29:00.001-08:00

Do you want to be ccna certified.
do you want to begin your road to the world of cisco then you are in the true place.
this is the beginning of "Be ccna certified series " , our object is making ccna easy to you and give you skills you need to be achieve ccna certification :
first lets define CCNA Certification and what you need to be ccna Certified:
Network Associate (CCNA) validates the ability to install, configure, operate, and troubleshoot medium-size route and switched networks, including implementation and verification of connections to remote sites in a WAN. CCNA curriculum includes basic mitigation of security threats, introduction to wireless networking concepts and terminology, and performance-based skills. This new curriculum also includes (but is not limited to) the use of these protocols: IP, Enhanced Interior Gateway Routing Protocol (EIGRP), Serial Line Interface Protocol Frame Relay, Routing Information Protocol Version 2 (RIPv2),VLANs, Ethernet, access control lists (ACLs).
CCNA Prerequisites

No prerequisites

CCNA Exams
1- one exam :
640-802 CCNA
or
2- two exams

640-822 ICND1
640-816 ICND2

Exam Topics

The following topics are general guidelines for the content likely to be included on the Cisco Certified Network Associate exam.

Describe how a network works

Describe the purpose and functions of various network devices
Select the components required to meet a network specification
Use the OSI and TCP/IP models and their associated protocols to explain how data flows in a network
Describe common networked applications including web applications
Describe the purpose and basic operation of the protocols in the OSI and TCP models
Describe the impact of applications such as Voice Over IP on a network
Interpret network diagrams
Determine the path between two hosts across a network
Describe the components required for network and Internet communications
Identify and correct common network problems at layers 1, 2, 3 and 7 using a layered model approach
Differentiate between LAN/WAN operation and features

Configure, verify and troubleshoot a switch with VLANs and interswitch communications

Select the appropriate media, cables, ports, and connectors to connect switches to other network devices and hosts
Explain the technology and media access control method for Ethernet networks
Explain network segmentation and basic traffic management concepts
Explain basic switching concepts and the operation of Cisco switches
Perform and verify initial switch configuration tasks including remote access management
Verify network status and switch operation using basic utilities (including: ping, traceroute, telnet, SSH, arp, ipconfig), and SHOW & DEBUG commands
Identify, prescribe, and resolve common switched network media issues, configuration issues, auto negotiation, and switch hardware failures
Describe enhanced switching technologies (including: VTP, RSTP, VLAN, PVSTP, 802.1q)
Describe how VLANs create logically separate networks and the need for routing between them
Configure, verify, and troubleshoot VLANs
Configure, verify, and troubleshoot trunking on Cisco switches
Configure, verify, and troubleshoot interVLAN routing
Configure, verify, and troubleshoot VTP
Configure, verify, and troubleshoot RSTP operation
Interpret the output of various show and debug commands to verify the operational status of a Cisco switched network.
Implement basic switch security (including: port security, trunk access, management vlan other than vlan1, etc.)

Implement an IP addressing scheme and IP Services to meet network requirements in a medium-size Enterprise branch office network

Describe the operation and benefits of using private and public IP addressing
Explain the operation and benefits of using DHCP and DNS
Configure, verify and troubleshoot DHCP and DNS operation on a router (using both the CLI and SDM)
Implement static and dynamic addressing services for hosts in a LAN environment
Calculate and apply an addressing scheme including VLSM IP addressing to a network
Determine the appropriate classless addressing scheme using VLSM and summarization to satisfy addressing requirements in a LAN/WAN environment
Describe the technological requirements for running IPv6 in conjunction with IPv4 (including: protocols, dual stack, tunneling, etc).
Describe IPv6 addresses
Identify and correct common problems associated with IP addressing and host configurations

Configure, verify, and troubleshoot basic router operation and routing on Cisco devices

Describe basic routing concepts (including: packet forwarding, router lookup process)
Describe the operation of Cisco routers (including: router bootup process, POST, router components)
Select the appropriate media, cables, ports, and connectors to connect routers to other network devices and hosts
Configure, verify, and troubleshoot RIPv2
Access and utilize the router to set basic parameters.(including: CLI/SDM)
Connect, configure, and verify operation status of a device interface
Verify device configuration and network connectivity using ping, traceroute, telnet, SSH or other utilities
Perform and verify routing configuration tasks for a static or default route given specific routing requirements
Manage IOS configuration files. (including: save, edit, upgrade, restore)
Manage Cisco IOS
Compare and contrast methods of routing and routing protocols
Configure, verify, and troubleshoot OSPF
Configure, verify, and troubleshoot EIGRP
Verify network connectivity (including: using ping, traceroute, and telnet or SSH)
Troubleshoot routing issues
Verify router hardware and software operation using SHOW & DEBUG commands.
Implement basic router security

Explain and select the appropriate administrative tasks required for a WLAN

Describe standards associated with wireless media (including: IEEE, WI-FI Alliance, ITU/FCC)
Identify and describe the purpose of the components in a small wireless network. (Including: SSID, BSS, ESS)
Identify the basic parameters to configure on a wireless network to ensure that devices connect to the correct access point
Compare and contrast wireless security features and capabilities of WPA security (including: open, WEP, WPA-1/2)
Identify common issues with implementing wireless networks. (Including: Interface, misconfiguration)

Identify security threats to a network and describe general methods to mitigate those threats

Describe today's increasing network security threats and explain the need to implement a comprehensive security policy to mitigate the threats
Explain general methods to mitigate common security threats to network devices, hosts, and applications
Describe the functions of common security appliances and applications
Describe security recommended practices including initial steps to secure network devices

Implement, verify, and troubleshoot NAT and ACLs in a medium-size Enterprise branch office network

Describe the purpose and types of ACLs
Configure and apply ACLs based on network filtering requirements using SDM and CLI
Configure and apply an ACL to limit telnet and SSH access to the router using SDM and CLI
Verify and monitor ACLs in a network environment
Troubleshoot ACL issues
Explain the basic operation of NAT
Configure NAT for given network requirements using SDM and CLI
Troubleshoot NAT issues

Implement and verify WAN links

Describe different methods for connecting to a WAN
Configure and verify a basic WAN serial connection
Configure and verify Frame Relay on Cisco routers
Troubleshoot WAN implementation issues
Describe VPN technology (including: importance, benefits, role, impact, components)
Configure and verify a PPP connection between Cisco routers

Password Recovery Procedure for the Cisco 2600 and 2800 Series Routers

2011-11-16T09:04:00.001-08:00

Introduction

This document describes how to recover the enable password and the enable secret passwords. These passwords protect access to privileged EXEC and configuration modes. The enable password password can be recovered, but the enable secret password is encrypted and must be replaced with a new password. Use the procedure described in this document in order to replace the enable secret password.

The information in this document is based on these hardware versions:

Cisco 2600 Series Router
Cisco 2800 Series Router

Step-by-Step Procedures

This section describes two procedures to recover your passwords.

Procedure 1

Complete these steps in order to recover your password:

Attach a terminal or PC with terminal emulation to the console port of the router.
Use these terminal settings:
- 9600 baud rate
- No parity
- 8 data bits
- 1 stop bit
- No flow control
If you can access the router, type show version at the prompt, and record the configuration register setting.
Note: The configuration register is usually set to 0x2102 . If you can no longer access the router , you can safely assume that your configuration register is set to 0x2102.
Use the power switch in order to turn off the router, and then turn the router back on.
Press Break on the terminal keyboard within 60 seconds of power up in order to put the router into ROMmon.
Type confreg 0x2142 at the rommon 1> prompt in order to boot from Flash.
This step bypasses the startup configuration where the passwords are stored.
Type reset at the rommon 2> prompt.
The router reboots, but ignores the saved configuration.
Type no after each setup question, or press Ctrl-C in order to skip the initial setup procedure.
Type enable at the Router> prompt.
You are in enable mode and should see the Router# prompt.
Type configure memory or copy startup-config running-config in order to copy the nonvolatile RAM (NVRAM) into memory.
Warning: Do not type copy running-config startup-config or write. These commands erase your startup configuration.
Type show running-config.
The show running-config command shows the configuration of the router. In this configuration, the shutdown command appears under all interfaces, which indicates all interfaces are currently shut down. In addition, the passwords (enable password, enable secret, vty, console passwords) are in either an encrypted or unencrypted format. You can reuse unencrypted passwords. You must change encrypted passwords to a new password.
Type configure terminal.
The hostname(config)# prompt appears.
Type enable secret <password> in order to change the enable secret password. For example:
```
hostname(config)#enable secret cisco
```
Issue the no shutdown command on every interface that you use.
If you issue a show ip interface brief command, every interface that you want to use should display up up.
Type config-register <configuration_register_setting>. Where configuration_register_setting is either the value you recorded in step 2 or 0x2102 . For example:
```
hostname(config)#config-register 0x2102
```
Press Ctrl-z or end in order to leave the configuration mode.
The hostname# prompt appears.
Type write memory or copy running-config startup-config in order to commit the changes.

Procedure 2

Complete these steps in order to recover your password:

Shut down the router.
Remove the compact flash that is at the back of the router.
Power on the router.
Once the Rommon1> prompt appears, enter this command:
```
confreg 0x2142
```
Insert the compact flash.
Type reset.
When you are prompted to enter the initial configuration, type No, and press Enter.
At the Router> prompt, type enable.
At the Router# prompt, enter the configure memory command, and press Enter in order to copy the startup configuration to the running configuration.
Use the config t command in order to enter global configuration mode.
Use this command in order to create a new user name and password:
```
router(config)#username cisco privilege 15 password cisco
```
Use this command in order to change the boot statement:
```
config-register 0x2102
```
Use this command in order to save the configuration:
```
write memory
```
Reload the router, and then use the new user name and password to log in to the router.

for more details :http://www.cisco.com/en/US/products/hw/routers/ps259/products_password_recovery09186a0080094675.shtml

Abstract of CCNA study guide-11 - VLSM

2011-11-14T07:47:00.001-08:00

Continue the series of Abstract CCNA study guide book .

Variable Length Subnet Masks (VLSMs)

I’m going to show you a simple way to take one network and create many networks using subnet masks of different lengths on different types of network designs. This is called VLSM networking, and it does bring up another subject I mentioned at the beginning of this chapter: classful and classless networking.

All hosts and router interfaces have the same subnet mask, this is called classful routing. And if we want this network to be more efficient, we definitely need to add different masks to each router interface and this is called classless routing.

we use what are referred to as Variable Length Subnet Masks (VLSMs) to provide only the needed number of hosts on each router interface

Implementing VLSM Networks

To create VLSMs quickly and efficiently, you need to understand how block sizes and charts work together to create the VLSM masks. Table 3.3 shows the block sizes used when creating VLSMs with Class C networks.

Prefix	Mask	Hosts	Block Size	Subnets
/25	128	126	128	2
/26	192	62	64	4
/27	224	30	32	8
/28	240	14	16	16
/29	248	6	8	32
/30	252	2	4	64

For example, if you need 25 hosts, then you’ll need a block size of 32. If you need 11 hosts, you’ll use a block size of 16. Need 40 hosts? Then you’ll need a block of 64.

The next step is to create a VLSM table. Next Figure shows you the table used in creating a VLSM network. The reason we use this table is so we don’t accidentally overlap networks.

Notice that the block sizes are listed starting from a block size of 4 all the way to a block size of 128. If you have two networks with block sizes of 128, you’ll quickly see that you can have only two networks. With a block size of 64, you can have only four networks, and so on.

Now, just fill in the chart in the lower-left corner, and then add the subnets to the worksheet and you’re good to go.

So let’s take what we’ve learned so far about our block sizes and VLSM table and create a VLSM using a Class C network address 192.168.10.0 for the network in Figure below. Then fill out the VLSM table, as shown in Figure .

In Figure 3.6, we have four WAN links and four LANs connected together. We need to create a VLSM network that will allow us to save address space. Looks like we have two block sizes of 32, a block size of 16, and a block size of 8, and our WANs each have a block size of 4. Take a look and see how I filled out our VLSM chart in Figure below .

Summarization

Summarization, also called route aggregation, allows routing protocols to advertise many networks as one address. The purpose of this is to reduce the size of routing tables on routers to save memory, which also shortens the amount of time for IP to parse the routing table and find the path to a remote network.

Next Figure shows how a summary address would be used in an internetwork.

all you need to have down are the block sizes that we just used in learning subnetting and VLSM design. For example, if you wanted to summarize the following networks into one network advertisement, you just have

to find the block size first; then you can easily find your answer: 192.168.16.0 through network 192.168.31.0

What’s the block size? There are exactly 16 Class C networks, so this neatly fits into a block size of 16.

Okay, now that you know the block size, you can find the network address and mask used to summarize these networks into one advertisement. The network address used to advertise the summary address is always the first network address in the block—in this example, 192.168.16.0. To figure out a summary mask, in this same example, what mask is used to get a block size of 16? Yes, 240 is correct. This 240 would be placed in the third octet—the octet where we are summarizing. So, the mask would be 255.255.240.0.

Here’s another example: Networks 172.16.32.0 through 172.16.50.0

This is not as clean as the previous example because there are two possible answers, and here’s why: Since you’re starting at network 32, your options for block sizes are 4, 8, 16, 32,64, etc., and block sizes of 16 and 32 could work as this summary address.

_ Answer #1: If you used a block size of 16, then the network address is 172.16.32.0 with a mask of 255.255.240.0 (240 provides a block of 16). However, this only summarizes from 32 to 47, which means that networks 48 through 50 would be advertised as single networks. This is probably the best answer, but that depends on your network design.

Let’s look at the next answer.

_ Answer #2: If you used a block size of 32, then your summary address would still be 172.16.32.0, but the mask would be 255.255.224.0 (224 provides a block of 32). The possible problem with this answer is that it will summarize networks 32 to 63 and we only have networks 32 to 50. No worries if you’re planning on adding networks 51 to 63 later into the same network, but you could have serious problems in your internetwork if somehow networks 51 to 63 were to show up and be advertised from somewhere else in your

network! This is the reason why answer number one is the safest answer.

Let’s take a look at another example, but let’s look at it from a host’s perspective.

Your summary address is 192.168.144.0/20—what’s the range of host addresses that would be forwarded according to this summary? The /20 provides a summary address of 192.168.144.0 and mask of 255.255.240.0. The third octet has a block size of 16, and starting at summary address 144, the next block

of 16 is 160, so our network summary range is 144 to 159 in the third octet (again, you must

be able to count in 16s!).

Figure below , the Ethernet networks connected to router R1 are being summarized to R2 as 192.168.144.0/20. Which range of IP addresses will R2 forward to R1 according to this summary?

No worries—this is really an easier question than it looks. The question actually has the summary address listed: 192.168.144.0/20. You already know that /20 is 255.255.240.0, which means you’ve got a block size of 16 in the third octet. Starting at 144 (this is also right there in the question), the next block size of 16 is 160, so you can’t go above 159 in the third octet. The IP addresses that will be forwarded are 192.168.144.1 through 192.168.159.255. (Yes, the broadcast address is forwarded.)

Okay, last one. In next Figure, there are five networks connected to router R1. What’s the best summary address to R2?

I’m going to be honest—this is a much harder question than the one in Figure 3.15. You’re going to have to look pretty hard to see the answer. The first thing to do with this is to write down all the networks and see if you can find anything in common with all six:

_ 172.1.4.128/25 , 172.1.7.0/24 , 172.1.6.0/24 , 172.1.5.0/24 , 172.1.4.0/24

Do you see an octet that looks interesting to you? I do. It’s the third octet. 4, 5, 6, 7, and yes, it’s a block size of 4. So you can summarize 172.1.4.0 using a mask of 255.255.252.0,which means you will use a block size of 4 in the third octet. The IP addresses forwarded with this summary are 172.1.4.1 through 172.1.7.255.

Troubleshooting IP Addressing

Let’s use next Figure as an example of your basic IP trouble—poor Sally can’t log in to the Windows server.

Here are the four troubleshooting steps Cisco recommends:

1. Open a DOS window and ping 127.0.0.1. This is the diagnostic, or loopback, address, and if you get a successful ping, your IP stack is considered to be initialized. If it fails, then you have an IP stack failure and need to reinstall TCP/IP on the host.

2. From the DOS window, ping the IP address of the local host. If that’s successful, your network interface card (NIC) is functioning. If it fails, there is a problem with the NIC. Success here doesn’t mean that a cable is plugged into the NIC, only that the IP protocol stack on the host can communicate to the NIC (via the LAN driver).

3. From the DOS window, ping the default gateway (router). If the ping works, it means that the NIC is plugged into the network and can communicate on the local network. If it fails, you have a local physical network problem that could be anywhere from the NIC to the router.

4. If steps 1 through 3 were successful, try to ping the remote server. If that works, then you know that you have IP communication between the local host and the remote server

If the user still can’t communicate with the server after steps 1 through 4 are successful, you probably have some type of name resolution problem and need to check your Domain Name System (DNS) settings. But if the ping to the remote server fails, then you know you have some type of remote physical network problem and need to go to the server and work through steps 1 through 3 until you find the snag.

Before we move on to determining IP address problems and how to fix them, I just want to mention some basic DOS commands that you can use to help troubleshoot your network from both a PC and a Cisco router .

Packet InterNet Groper (ping) Uses ICMP echo request and replies to test if a node IP stack is initialized and alive on the network.

traceroute Displays the list of routers on a path to a network destination by using TTL time-outs and ICMP error messages. This command will not work from a DOS prompt.

tracert Same as traceroute, but it’s a Microsoft Windows command and will not work on a Cisco router.

arp -a Displays IP-to-MAC-address mappings on a Windows PC.

show ip arp Same command as arp -a, but displays the ARP table on a Cisco router.

ipconfig /all Used only from a DOS prompt, shows you the PC network configuration.