Networking Gurus

How to configure EtherChannel ?

noreply@blogger.com (Rajesh kanna) — Fri, 14 Sep 2012 19:07:00 +0000

Previous post describes how EtherChannel works and why we use it.
Take a look here

Now we’ll discuss how to configure EtherChannel.

As we seen before, we can bundle up to 8 physical interfaces. We must bind the number of physical interfaces into one logical interface (Channel). Most of the Cisco switches support 64 channels. Single channel can bind min 2 to max 8 physical interfaces.

PAgP and LACP are the two different Protocols which facilitates the automatic creation of EtherChannels by Exchanging packets between Ethernet interfaces.

PAgP is a Cisco proprietary protocol whereas LACP is an open standard protocol 802.3ad

Two types of EtherChannel Configuration:

1. 1. Layer 3 Configuration: In Layer 3 EtherChannel Configuration, first we must create a logical interface which is call Port-Channel. Then we add the physical interfaces to the Port-Channel.

Example to create a Port-Channel:

Router# configure terminal

Router(config)# interface port-channel 6 (port-channel number 1-64)

Router(config-if)# ip address 10.0.0.1 255.0.0.0

Router(config-if)# exit

Router(config)# exit

Router# show running-config interface port-channel 6 (to verify the port-channel configuration)

We created a port-channel successfully. Now we must add the physical interfaces to this port-channel 6.

Router# configure terminal

Router(config)# interface range fastethernet 1/1 -2

Router(config-if)# no ip address

Router(config-if)# channel-group group 6 mode desirable (by-defalut Cisco devices use PAgP)

Router(config-if)# exit

Router# show running-config interface fastethernet 1/1 (to verify interface 1 configuration)

Router# show interfaces fastethernet 1/1 etherchannel

2. 2. Layer 2 Configuration: Command varies in Layer 2. We manually created port-channel in Layer 3, but in Layer 2 we must create a channel-group which automatically assigns logical port-channel.

Example to create a channel-group:

Switch(config)#interface range fastethernet 1/1 - 4

Switch (config-if-range)#channel-group 1 mode on (Port 1/1-4 assigned to port-channel)

Switch (config-if-range)#switchport

Switch (config-if-range)#switchport trunk encapsulation dot1q

Switch (config-if-range)#switchport mode trunk

Switch #show interfaces port-channel 1

Switch #show etherchannel 1 summary

In the above example we assigned the ports as trunk. The ports with in a EtherChannel must be in trunk mode or in a single VLAN.

Whatever change of configurations made on port-channel must affect all the ports within the channel, but configuring an interface (port) only affects the particular interface not the port-channel.

How does EtherChannel works ?

noreply@blogger.com (Rajesh kanna) — Wed, 12 Sep 2012 10:12:00 +0000

EtherChannel is used to bundle multiple interface links into a single logical link. In a single EtherChannel we can add up to 8 interfaces.

What is the use of EtherChannel, why do i bundle multiple links into one?

If we have a fast Ethernet switch which has the speed of 100 Mbps per interface (port). Our workload and data stream is increasing day by day. Now what to do if 100 Mbps is not enough to forward our data stream? Simple, sell the fast Ethernet switch on eBay and get one brand new Cisco Gigabit EtherChannel switch. ;)

Replacing the Hardware is not always the best thing to do. What if the same issue happens to a guy who got Gigabit EtherChannel switch? To overcome this problem EtherChannel is used to bundle multiple fast Ethernet interface in to one.

In a fast Ethernet switch speed of an interface is up to 100 Mbps, if we bundle 8 interfaces in to one, we get the total speed of 800 Mbps. In Gigabit EtherChannel a bundle of 8 interfaces gives the speed up to 8 Gbps.

Now what if a single link in an EtherChannel goes down? Nothing happens, still the bundle works fine with the rest of the 7 links (800-100 = 700) which has the speed of 700 Mbps.

Spanning Tree Protocol (STP) considers the bundled EtherChannel has a single link, so link failure inside the bundle doesn’t affect the STP to recalculate the redundancy.

We can create EtherChannel for Layer2 interface and also for Layer3 interface. Configuring method is different. All the interfaces in an EtherChannel must be configured as either Layer 2 or Layer 3 interfaces. All interfaces in an EtherChannel must be in same speed.

How to configure EtherChannel ?

How to Configure HSRP v2 ?

noreply@blogger.com (Rajesh kanna) — Mon, 10 Sep 2012 04:28:00 +0000

There's no much difference between configuring HSRP v1 & HSRP v2. HSRP version 2 will not interoperate with HSRP version 1. HSRP v1 & 2 won't work in same interface. But we can configure v1 in one interface and v2 in another interface of the same router. Group number has been extended in version 2. version 1 supports (0 - 255) whereas, version 2 supports (0 - 4095)

New features in HSRP v2

HSRP version 2 Group range has been extended 0 through 4095.

Version 1 timer values are advertised and learned in seconds, it doesn't support millisecond timers. In v2 millisecond timer values added an advantage.

HSRP v 2 uses the new IP multicast address 224.0.0.102 to send hello packets instead of 224.0.0.2, which is used by version 1.

In v1 we can't identify the source of the hello packet, because router uses HSRP virtual MAC address as it's source address, which doesn't contain interface address. HSRP v2 includes a 6-bye identifier field which includes the MAC address of the local interface.

MAC address range 0000.0C9F.F000 to 0000.0C9F.FFFF.

v2 cannot inter-operate with v1 because version 2 has a different packet format than v1.

Configuration Methods :

Step 1 : Router > enable

Step 2 : Router# configure terminal

Step3 : Router(config)#interface vlan100

Step4 : Router(config-if)# ip address 192.168.1.1 255.255.255.0

Step 5 : Router(config-if)# standby version 2 ( it shows we changed v1 to v2 )

Step 6 : Router(config-if)# standby 100 ip 192.168.1.100
( in HSRP v2 the range of group number is extended to 0 - 4095)

Step 7 : Router(config-if)# end

CCNP (Routing Labs)

noreply@blogger.com (Rajesh kanna) — Mon, 17 Oct 2011 08:07:00 +0000

Given below is the CCNP Routing GNS3 Sim, I created it for my exam. It's 1.05 GB in size and compressed to 586KB. For further details about CCNP Lab questions visit www.digitaltut.com

To open the Sim, Right click --> topology.net --> open with notepad--> change the path where you have c7200.bin file in your drive.

For IPv6 Sim i used c2691-adventerprisek9-mz.124-5a.image
you can use either .image or .bin fine. Make the change in topology.net

Download CCNP Routing Lab.

Please leave comments...

Head Office to Branch Office 1 & Branch Office 2

noreply@blogger.com (Rajesh kanna) — Wed, 11 May 2011 10:26:00 +0000

Establishing connection between Head Office to Branch Office 1 and Branch Office 2

Head office to Branch office Routing

noreply@blogger.com (Rajesh kanna) — Wed, 11 May 2011 08:21:00 +0000

Establishing simple Static connection between Head office and Branch office

Next: Head office & Two Branch office using three routers.

Setting Password ( Cisco Router)

noreply@blogger.com (Rajesh kanna) — Sat, 16 Apr 2011 17:05:00 +0000

Next: How to establish communication between Head office and Branch office.

How to work with Cisco Packet Tracer

noreply@blogger.com (Rajesh kanna) — Sat, 16 Apr 2011 17:00:00 +0000

Next: How to set Password for Cisco Routers

CLI Modes of Cisco routers

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 20:01:00 +0000

User EXEC: Router >

This is a restricted mode. Here we can’t make changes or configure the router. In this mode users are only allowed to execute some commands like Ping IP address. We are not allowed to reload the router here. To exit from this mode type “logout” or “exit” command.

"Please Click the image"

Privileged EXEC: Router #

From the User EXEC mode the “enable” command takes us to the privileged mode which we have few rights to control the router. Here we can verify the configuration made in the router and also allows us to troubleshoot. Here we can configure router’s date and time and also we can manage configuration files. To exit from this mode types “disable” or “exit” command.

Global Configuration Mode: Router(config-if)#

From the privileged mode the “configuration terminal” command takes us to the global configuration mode. This is the place where we can completely configure the router. To exit from this mode type “exit” command.

Routing Logic

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 18:13:00 +0000

Routers are used to Communicate Systems from different TCP/IP areas.

Imagine that you are in Head Office, if you want to communicate with a person who is inside your Network (LAN) then Routers are not necessary unless your network is Sub-netted. But if you are trying to communicate with your Branch Office which is located 500 Km out from the Head Office, now you need the help of Routers.

Whenever any packet comes to the router where the destination IP address is not its own IP address the routers overwork of seeing the routing table and then forward the packet to the concern person. So the routers do IP routing.

After we configure the router, we configure all the systems in our network with a default gateway which is the router’s IP address. When the default gateway is added a default route gets added in the routing table. When the IP protocol does route it applies a default route only when there is no specific route available for that network destination. Routers also route the packet only when they have a matching route in the routing table, if the route is not available then routers drop the packet and generates an ICMP error message.

Before the transmission takes place data's were divided into several packets, each packet may take a different route to reach the destination, which we called as packet switching.

Click the image to view How the packet travels.

What is Router?

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 17:13:00 +0000

Router is a Layer 3 (Network Layer) device which means it works at first three layers of OSI Model (Physical Layer, Data Link Layer, Network Layer). Routers use the method called Packet Switching to transfer data from one place to another place on Network. Computers use its Operating System (OS) to work likewise Routers use its Internetwork Operating System (IOS) to work.

Cisco Packet Tracer

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 12:10:00 +0000

Cisco Packet Tracer is a powerful network simulation program that allows students to experiment with network behavior and ask “what if” questions. As an integral part of the Networking Academy comprehensive learning experience, Packet Tracer provides simulation, visualization, authoring, assessment, and collaboration capabilities and facilitates the teaching and learning of complex technology concepts.

Packet Tracer supplements physical equipment in the classroom by allowing students to create a network with an almost unlimited number of devices, encouraging practice, discovery, and troubleshooting. The simulation-based learning environment helps students develop 21st century skills such as decision making, creative and critical thinking, and problem solving.

Packet Tracer complements the Networking Academy curricula, allowing instructors to easily teach and demonstrate complex technical concepts and networking systems design. The software is available free of charge to all Networking Academy instructors, students, and alumni.

Download Packet Tracer

GNS3

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 12:04:00 +0000

GNS3 is a graphical network simulator that allows simulation of complex networks.

To allow complete simulations, GNS3 is strongly linked with :

* Dynamips, the core program that allows Cisco IOS emulation.
* Dynagen, a text-based front-end for Dynamips.
* Qemu, a generic and open source machine emulator and virtualizer.

GNS3 is an excellent complementary tool to real labs for network engineers, administrators and people wanting to pass certifications such as CCNA, CCNP, CCIP, CCIE, JNCIA, JNCIS, JNCIE.

It can also be used to experiment features of Cisco IOS, Juniper JunOS or to check configurations that need to be deployed later on real routers.

This project is an open source, free program that may be used on multiple operating systems, including Windows, Linux, and MacOS X.

Download GNS3

How does the OSI Model function?

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 08:03:00 +0000

OSI Model is a combination of Seven Layers which we already discussed. Now how those layers works for communication through Network, this works in a form called Encapsulation and Decapsulation.

Data sending end encapsulates the data and receiving end Decapsulates the data.

Encapsulation:

In the above example the data from the computer has been sent through Internet to another computer. Application Layer is which user work assume that we are sending Mail to our friend. The data is now sent to Presentation Layer.

Presentation Layer converts the data to ANSII coded file which the other computer can understand. Then the data sent to Session Layer and then to Transport Layer.

Transport Layer cuts the data in to several pieces and Sequence Number is been added to each piece in order to rearrange it properly by the receiving end. Then TCP header is added this encapsulated part is called Segment. Now the segment is sent to Network Layer.

Network Layer adds from address and to address which we call Source IP address and Destination IP Address in order to route the packet through the internet. In this layer the encapsulated data is called Packet. Then packet is sent to Data Link Layer.

Data Link Layer encapsulates the Packet with Source and Destination MAC Address and at the end FCS (Frame Check Sequence) for error checking is also added. This type of encapsulated data is called Frame. Now the frame is sent to Physical Layer.

Physical Layer converts the frame into digital signal which can transmit through the Network Cable. Now the data has been sent through the Physical Medium.

Decapsulation:

Decapsulation is the process which happens at the receiving end.

Physical Layer receives the signal that we sent in the previous section, now the signal is converted to frame and sent to its upper layer which is Data Link Layer.

Data Link Layer checks the MAC Address to confirm that this frame has been sent to this computer, after confirmation it performs the CRC (Cyclic Redundancy Check) to know the frame is corrupted or received properly. Then the information that was added by the remote Data Link Layer has been removed and sends the packet to Network Layer.

Network Layer verifies the IP address in the packet with its own IP, if it matches then the remote Network Layers information has been removed and sends the Segment to Transport Layer.

Transport Layer rearranges the Segment with its Sequence Number and sends an Acknowledgement to Remote computer that it received the data properly or not. Here TCP is used for the transmission, click here to know more about TCP. Then data has been sent to its upper layer, so that the user received the Mail that was sent by us in the previous section. :)

IP (Internet Protocol)

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:59:00 +0000

TCP/IP is the commonly known protocol, we already discussed about TCP. Now what is IP and what it does?

Internet Protocol (IP) is used for routing packets. TCP & IP works together to communicate through internet but they works at different layer. IP works at Network Layer (Layer 3) where routing and forwarding takes place. IP is the main Protocol at Network Layer. We know how TCP works, it chops the data in to several pieces and adds Sequence Number in order to rearrange it properly, but who says that these pieces must be delivered to whom?

That’s what IP says :)

When the segments are ready to go then it reaches the Network Layer, Internet Protocol Adds an IP Header which contains the Source IP Address and Destination IP Address so now the packets can travel through the internet. It’s same as we sending Mail with From Address and To Address. All the sending Packets doesn’t travel in the same route, it takes different route but to reach the same destination.

TCP (Transmission Control Protocol)

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:57:00 +0000

Transmission Control Protocol (TCP) is the major transport protocol because of its reliability. TCP is a layer 4 protocol which lies at transport layer. It is a connection oriented protocol which establishes a logical connection between source and destination computers before it transfers data.

For Example:

We make a phone call to contact a person, but we only Start our conversation if the person other side picked up the phone.

Same as the above example TCP first establishes connection between the computers. TCP is an end to end reliable protocol which takes responsible for whether the sent data is received by the other end by exchanging Acknowledgment (ACK).

Whenever a TCP Packet is sent, the acknowledgement is returned from the received end.

Getting into detail

The data we supposed to send will be chopped into several pieces, the pieces were loaded into containers for transport, and the containers are which we called Segments.

There is a limitation that how much of data should the segment carry at one go. This size keeps on changing according to the Network condition which is called Flow Control.

Each and every segments sent by System A are identified by a number called Sequence Number which helps the receiving end to rearrange the data in its original order.

The above Picture shows how TCP establishes Connection before Communication takes Place.

Step 1: TCP of A informs B with SYNC flag ON that I want to start sending segments from Sequence No: 300 so keep track on it. Acknowledgement is 0 because this is the first packet that A transfers, it hadn’t received any packets before from B to Acknowledge.

Step 2: B replies back with SYNC flag ON that I got your 300 send me 301. I want to start sending segments from Seq No: 700 so keep track on it.

Step 3: I got your 700 so you can start sending 701.

This is called Sequence Number SYNC (or) 3 Way Handshake.

Switch

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:51:00 +0000

Switch is used to connect multiple Computers in a Local Area Network same as the Hub does. Then why we need Switch instead of Hub?

Switch is an intelligent device whereas Hub got no intelligence. Switch is a Layer 2 device which works at Data Link layer of OSI Model. Layer 2 can recognize MAC Address.

Switch maintains its own MAC Address table which remembers the Computers MAC.

Sys A sends data to Sys D, when Switch receives the signal from Sys A it saves the MAC Address of Sys A and it has no idea about Sys D MAC so it simply forwards the signal as Broadcast via all other ports.

Now Sys D sending reply to Sys A, when Switch receives the signal it saves the MAC of Sys D in the table and now it knows Sys A is located at Port 1 so forwards the signal only via Port 1.

Likewise Switch remembers all the MAC Address of the Computers. This method saves Bandwidth and prevents from the collision.

Modem

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:44:00 +0000

A Modem (Modulator-Demodulator) is used to translate Analog signal to Digital signal and Digital to Analog signal.When the Internet started to spread all over the world, it is hard to lay separate cable for every one who needs internet, so to solve this problem existing telephone lines are used. But telephone lines are supposed to carry Analog signals to transmit our voice, whereas Computers can only recognize Digital signals.

We need a translator who can translate Analog signals to Digital which computers can recognize, Digital to Analog signal which the telephone lines can carry. Modem is the translator here.

Hub

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:43:00 +0000

Hub is used to connect multiple computers in a single Network. It’s a Layer 1 (Physical Layer) device which simply Broadcasts the receiving signal.

Example:

Here Sys A sends a data to Sys D, when hub receives the signal from Sys A it forwards the signal via all the other ports. Now all the Computers connected in Hub except Sys A will receive the data but only Sys D will pick it. Hub is commonly known as a stupid Device, because it simply broadcasts the signal all over the network that makes the bandwidth down and causes Collision.

Protocol

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:40:00 +0000

Protocol plays vital role in communication. Protocol is a set of rules, which leads the communication between multiple computers over the Network. It instructs the sender and receiver end while the communication takes place. IP, TCP, UDP, FTP, and HTTP these are some Major protocols.

Example:

Hyper Text Transfer Protocol (HTTP)

You can see "http://" at the URL bar of a web browser, which grabs the site for you.

Unicast and Multicast

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:37:00 +0000

I Hope you know what Broadcast is, if not Click Here

Unicast: (One to One)

This is simple like we know to whom we have to talk, so we just go and talk.

Computer knows the destination IP address, so it transfers the data directly to the concern computer.

Multicast: (One to Many)

To understand in a simple way, we forward a text message to our friends list, which means at a single transmission the text message has been sent to the persons only in our friends list.

Example: A Computer sends data to all the computers in a particular group only, the Computers out from that group won’t receive the data.

Class D IP is used for multicasting. Multicasting is much used between routers to make relation with each other.

Broadcast

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:35:00 +0000

Here I gave a brief explanation just to understand what Broadcast means.

Broadcast: (One to All)

This is a way to find the right person to communicate. To understand, if we want to communicate with John but we don’t know who is John in the group before us. So we shout “Hey John”, everyone will hear what we shout but only john reply back “Hey it’s me”, then we start our communication with him.

Likewise if a computer don’t know the destination Address of which it has to establish communication, so it simply send a broadcast, every computer in the local network receives the broadcast and only the concern computer reply back.

Limited Broadcast:

If a destination MAC address looks like FF: FF: FF: FF: FF: FF then it will be forwarded to all the computers in the Network, it’s a Broadcast MAC address.

Broadcast IP must be set to 255.255.255.255 which means the packet will be forwarded to all computers in the Network.

This type of Broadcast Never crosses over the router.

Directed Broadcast:

It broadcasts only to a specified Networks Computer. This type of Broadcast crosses over the router. In this type of Broadcast only the host part of IP is defined as 255.

Example:

10.0.0.0 /24 – It means the last octet is Host part

So Broadcast address for this Network is 10.0.0.255

ARP and RARP

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:29:00 +0000

Address Resolution Protocol (ARP) is used to identify the hardware address (MAC) of a particular IP. For Computers on Network simply an IP Address is not enough to communicate, they need MAC address which is a layer 2 address whereas IP is a layer 3 address.

FF-FF-FF-FF-FF-FF - Broadcast, this data will spread all over the Local Area Network , which host has the IP 192.168.1.2 will pick the data and reply back it’s MAC to the Source address.

My IP – Source IP

Your IP - Destination

As per the above picture User A wants to communicate with User B, before the communication takes place ARP generates a request to the local network to know the MAC address of User B which is a Broadcast. Reply from the User B is Unicast. Once User A receives the MAC address it stores in ARP Cache Memory.

To see ARP Cache:

Start => Run => type cmd

C:\> ARP -a

What is OSI Model ?

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:08:00 +0000

Open System Interconnection Model (OSI) which is the basic and most important concept to understand in Networking. OSI Model consists of seven layers, each layer is designed for specific Networking task. These layers refer how the communication between several systems has to be done. OSI Model is the Standard way of communication on Network.

Encapsulation: The process of adding the layer covers.

De-multiplexing: The process of removing layer covers.

Physical Layer:

This is the first layer of OSI Reference Model. Physical Layer is the communication medium where multiple systems physically connected with each other. It’s responsible for transmission.

Data Link Layer:

It is Responsible for MAC, Identification, Error detection, Collision Management. It transfers the frame through Physical Layer. Switch operates at this layer.

Network Layer:

Packet Switching takes place here. Network Layer routes the data across the network. Internet Protocol (IP) works at this layer. Routers work at this Layer, which we call Layer 3 devices.

Transport Layer:

It is responsible for delivering data to the host computers. Transport Layer Provides reliability, flow control, which helps to avoid congestion during the data transmission. Transmission Control Protocol (TCP), User Datagram Protocol (UDP) works at this layer.

Session Layer:

Session Layer remembers the context, like which program you are working at, so that it makes to get the related reply easily. Session layer understand which particular context coming from which particular system.

Presentation Layer:

In a simple way it acts like a translator. Which means it presents the data in a way which helps the other system on the network able to understand it easily. Data compression and decompression, encryption and decryption performed here.

Application Layer:

It is the top most layer of the OSI Model. The application layer provides the environment for application data to be carried from one place to another. This means if we are working at web browser that data must be carried by HTTP. HTTP, FTP, Telnet, POP3, SMTP are some protocols works at this layer.

How does the OSI Model functions.

What is MAC Address ?

noreply@blogger.com (Rajesh kanna) — Thu, 14 Apr 2011 07:00:00 +0000

MAC address (Media Access Control) is also called as Physical address. It is an unique ID of Network Interface Card. It’s a 48 bit binary number, and it’s divided into two parts OUI & Unique Device ID. OUI must have 24 bit & Unique Device ID 24 bit. MAC address is always expressed in a Hexadecimal format. MAC address exists in the Second layer of the OSI Model (Data Link Layer). Every Computer has its unique MAC address. If you change your Network Card then your computer’s MAC address gets changed.

00 - 02 - B2 - 3D - 12 – 48

This part is specified Vendors Serial Number

By IEEE Group

To know your MAC address type ipconfig /all in cmd.

physical address is the MAC address.