Rhynobyte Technologies

BPDUGuard vs. BPDUFilter

2010-03-11T04:35:00.000-06:00

We all know that Spanning-Tree uses BPDU to communicate link state and configuration changes within a Switched network. Spanning-Tree will use 2 types of BPDU's:

TCN BPDU - will be used to notify other switches of changes occuring
Configuration BPDU - will be used for the spanning-tree computations

The main goal of the BPDU's is to assist in maintaining information regarding the link state of neighboring switches so that a loop free switched network can be maintained. The BPDU's help create the best reference point called the root bridge and helps create alternate pathing in case a link goes down.

So we know that switch ports connected to other switch ports will send each other BPDUs in order to assist spanning-tree, and the those switched ports will use the stp timers ( 2 sec hellos, 15 listening, 15 learning, 20 sec max age). Given the timers of spanning-tree it could take up to 50 seconds to recover from any link failures.

In order to bypass this 50 second delay, we can configure the switch to bypass the listen, learning, and max age timer by putting the interfaces in portfast mode.

Portfast mode should be used when end devices such as servers, router, and pc's are connecting to the switch. Spanning-tree is not necessary when connecting to such devices, only necessary when connecting switches to switches.

So why do we need BPDUGuard and BPDUFilter?

Well, what if we assigned a port to a user thinking he/she would plug in their pc, but instead they plugged in their Cisco swith they bought off of Ebay. That switch would immediately beging sending BPDU's to the other network switches.

Given that the root bridge switch is determined by a combination of both (port priority + mac address) called the bridge ID, this new switch could win the root election thus altering all of the switching behaviour of the entire network....not good.

To prevent such unexpected mayheim, you can configure BPDUGuard or BPDUfilter on those ports that have been set as portfast ports.

BPDUGuard will watch out for BPDU's on configured ports and if it senses any BPDU's, it will shut the port down and put it in errdisable status so that there is no way any new unathorized switch can begin sending BPDU's to the switch network and participation in spanning-tree.

BPDUFilter is very similar to BPDUGuard in that it watches for BPDU's but rather than shutting down the port it merely ignores the BPDU's and filters them out rather than shutting down the port and putting the port in errdisable.

BPDUGuard - shut ports down and puts ports in errdisable if it senses BPDU's
BPDUFilter - does not shut down port or put in errdisable but instead just filters (ignores) BPDU's

Routing Protocol Timers

2010-02-28T22:10:00.002-06:00

Routing Protocol Timers:

RIP

(update timer = 30 sec.) entire routing table

(invalid timer = 180 sec.)

(hold-down timer = 180 sec.)

(flush-down timer = 240 sec.)

IGRP

(update timer = 90 sec.)

(invalid timer = 270 sec.)

(hold-down timer = 280 sec.)

(flush-down timer = 630 sec.)

EIGRP

(5 Sec = Hello timer) 
(3 times Hello = Hold-timer)

(60 Sec. = Hello timer) NBMA less than T1 speed

(3 times Hello = Hold-timer)

(90 Sec. = Update timer)

(3 times Update timer = Invalid timer)

(7 times Update timer = Flush timer)

OSPF

(10 Sec. = Hello timer)

(30 Sec. NBMA = Hello timer)

(4 times Hello = Dead-interval)

(4 times NBMA Hello = NBMA Dead-interval)

How to Remove a Lsas.Blaster.Keylogger virus

2010-02-28T09:46:00.000-06:00

If you are finding that you browser is being hijacked by various websites being automatically loaded and your like "what the heck", then you may have the Lsas.Blaster.Keylogger virus. In order to remove the virus you will need to do the following.

Kill Spyware Processes 692527612.exe, 1313928688.exe, 1806188250.exe under task manager.
Get rid of Files and Folder
C:\Documents and Settings\All Users\Application Data\1929146152\1313928688.exe
C:\Documents and Settings\All Users\Application Data\1372029626\1806188250.exe
C:\Documents and Settings\All Users\Application Data\870894309\692527612.exe

How a Router Selects the Best Path

2010-02-22T23:23:00.001-06:00

It is important to understand how a router selects the best path to a destination.

When there are multiple routes to a destination, a route that has the "longest prefix" length is chosen.
E: 192.168.1.0 /27 via 10.1.1.1, serial1 <<<< this route will win
O: 192.168.1.0 /24 via 10.1.1.2, serial0
When there are multiple routes to a destination and the prefix is equal between the routes, then the lowest administrative distance will be chosen.
When there are multiple routes to a destination that have both the same prefix length and the same administrative distance, then the route with the lowest metric will be chosen.
If the multiple routes have the same prefix length, same administrative distance, and the same metric, then the route will be equally load balanced.

You must consider that directly connected networks have a metric of 0 and static routes using the next hop address will have a metric of 1. Static routes with a exit interface will have a metric of 0.

Here are the Administrative Distances that should be memorized:

Static routes using exit interface: 0
Directly connected routes: 0
Static routes with and next hop address: 1
EIGRP Summary routes: 5
External BGP: 20
Internal EIGRP: 90
IGRP: 100
OSPF: 110
External EIGRP: 170
Internal BGP: 200
Unknown networks 255

TCP/IP Review

2010-02-12T21:55:00.016-06:00

1. Name the 5 layers of TCP/IP protocol suite and each layers purpose?

The TCP/IP protocol suite has 5 layers not to be confused with the OSI model 7 layers. The upper 3 layers in the TCP/IP protocol suite is made up of the Application layer, Presentation layer, and the Session Layer altogether called the Application Layer or the 5th TCP/IP protocol suite Layer. The 4 lower layers of the TCP/IP suite consist of the Physical, Data, Network, and Transport.

-5 Application Layer ( Application Presentation Session)
-Application - allows access to network resources...ie...outlook..gmail...etc
-Presentation - prepares data by compressing, encrypting, or translate
-Session - establishes connections involving sockets

-4 Host-to-Host Layer - is responsible for delivery...upd and tcp

-3 Internet (IP) Layer - enables actual routing of data across a logical network by packet format and address format. Moves packets from source to destination.

-2 Data Layer - layer deals with the protocols (Ethernet, Frame-relay, ATM and SONET) that will control the data link layer.
Data link layer deals with:

-how the medium is accessed and shared *CSMA*
-how devices on the medium are identified *MAC address*
-how data is frame before being transformed on the medium

-1 Physical Layer - Transmission of bits over chosen medium and deals with electrical and mechanical specifications.

2. How many bits are in a ipv4 address and what is the most common version being used?

IPv4 is a 32 bit binary string. Depending on the class of the address some of the bits will be Network bits and some bits will be host bits. We will use subnet mask bits to distinguish the network bits from the host bits.

3. Explain Fragmentation?

Fragmentation is when the sending packet is larger than the Max Transmission Unit(MTU) of the data link that it is passing through. For example, if the original packet traversing the network is 3000 bytes in size, once it hits a data link that has an MTU of 1500 bytes, the packet will have to be fragmented into smaller packets. The router that placed the packet onto the data link will fragment the 3000 byte packet into 2 packets no larger than 1500 bytes in size each.

The router will use 3 fields to fragment the packet:
-Flags - 3 bit field. First bit is unused. Second bit is set to Don't Fragment (DF) bit. When the second bit is set to 1 then the router is instructed not to fragment the packet. It is important to know that when the packets cannot be fragmented then they will be dropped and an error message will be sent to the source. The third bit is the More Fragment (MF) bit and is set by the router when it fragments a packet. The router sets the MF bit to 1 in all of the fragments except the last fragment. By setting the MF bit to 1 the receiving device will continue to expect more fragments but when the MF bit is set to 0 the receiving device will no longer expect any more fragments for that packet.
-Fragmentation offset - 13 bit field that specifies the offset in units of 8 octets. Allows for packets to be reassembled in the correct sequencial order. This is especially important given that the fragments may not arrive in sequence. It is important to note that if a single fragment is lost during transmission then the entire packet must be resent and refragmented.
-Identifier - 16 bit field that will mark each fragment with the same number in the Identifier field so that the receiving device can understand which packets go together.

4. Explain Time to Live(TTL)?

Time to Live is designed to help packets from forever wandering around that network and being lost. TTL is an 8 bit field and it sets a certain number on each packet when orginally generated. Each router that passes the packet will decrement the packet by 1. Once the number reaches zero, the packet will be dropped/discarded and an error message will be sent to the source. TTL is just like hop count with a recommended value of 64.

5. What is the First Octet Rule?

Network addresses are broken up into classes. There are 4 octets each 8 bits long. Those 8 bit binary numbers are translated into more human friendly numbers. The first octet number will determine the class of the address. Example 192.168.1.50 is a class C address given that 192 falls in the class C range of addresses. So the First Octet Rule allows us to quickly determine which class the address belongs to.

Class A (1-126)
Class B (128-191)
Class C (192-223)

6. Show Class A, B, and C written in binary and decminal.

- Class A
*Binary form (00000000 - 01111111)
*Decimal form (1 - 127)
-Class B
*Binary form (10000000 - 10111111)
*Decimal form (1 - 127)
-Class C
*Binary form (11000000 - 11011111)
*Decimal form (1 - 127)

7. What is the Address Mask?

There are 32 bits in a Network Address broken up into 4 octets. The address mask will consist of 1's or 0's in binary. For example the address mask of the Class C network address 192.168.1.20 is 255.255.255.0 or in binary 11111111.11111111.11111111.00000000. The address simply separates the network bits from the host bits. The 255's in the example are the network and the 0 represents the hosts.

8. Explain a Subnet and why its use.

Given that each data link (network) and host will require unique identification, subnetting can be used to divide up each major address into subnetworks. This is done by using some of the host bits to become network bits. Example would be a Class A address of 10.0.0.0 255.0.0.0 being subnetted to 10.0.0.0 255.255.0.0. Notice that the subnet mask changed to 255.255.0.0. By adding all 1's (255) to the second octet of the subnet mask, we have just that easily changed the network portion of the network address to 10.0 leaving the remaining 16 bits to host address. A subnet is simply a subnetwork of a class A,B,or C network.

9. Explain why all O's or 1's cannot be used in a classful routing subnet environment.

Classful routing protocols (Rip ver1/IGRP) cannot distinguish between the network number and an all zero subnet. Classful routing protocols cannot distinguish between all 1's in the subnet and the network number either.
Classless protocols can recognize subnets with all 1's and 0's:
-RIP ver2
-EIGRP
-OSPF
-IS-IS
-BGP4

10. Describe ARP?

ARP is used to help devices discovered the data link identifier (mac address) of another device. In this case, ARP request will be encapsulated into the frame. ARP will map the discovered data link identifier to the IP address.

11. How does TCP provide connection oriented service?

TCP uses 3 mechanisms to assist TCP:
-labels packets with sequence numbers so that it can be properly ordered before delivery
-creates acknowledgements, checksums, and timer allowing sender and receiver to communicate regarding delivery of packets
-windowing allow the flow of packet delivery to be controlled

Bootmgr is compressed error

2010-01-31T00:30:00.000-06:00

I foolishly compressed my harddrive and forgot the Bootmgr will not work on a compressed harddrive. So after completely compressing my C:\ my computer would not boot correctly. At boot up I received a "Bootmgr is compressed" error. In order to fix the problem I had to pull out my Vista DVD and I did the following:

Boot the computer with the Vista DVD
Choose the "Repair my computer" option
Choose the Operating system installation and "load drivers"
Choose the drive that was compressed and deselect "compress this drive"
Reboot

802.1w - Spanning-Tree

2010-01-21T18:27:00.000-06:00

802.1w know as Rapid Spanning-Tree is a great improvement over 802.1d Spanning-Tree. 802.1w operates with the same principle of Spanning-Tree however the convergence time is dramatically faster.

Another added benefit of 802.1w(Rapid Spanning-Tree) is the fact that single or multiple instances can be applied. This can be done by applying RSTP with the Cisco proprietary PVST+ forming what's called RPVST+.

Just like 802.1d(Spanning-Tree) 802.1w(Rapid Spanning-Tree) chooses the Root Bridge based on the lowest Bridge ID.

Rapid Spaning-Tree Port Roles

Root Port - one port on each switch with best Root Path Cost to the Root Bridge
Designated Port - ports on the Root Bridge
Alternate Port - a different less desirable path to the Root Bridge and not the same as the Root Port
Backup Port - a port that creates a redundant path to an already connected segment

Spanning-Tree Root Bridge

2010-01-21T16:44:00.002-06:00

Spanning Tree Root Bridge

As soon as the switch powers up it first assumes that it is the Root Bridge. The Spanning Tree election process begins quickly given that BPDU's are sent out every 2 seconds. Every switch begins sending out BPDU's with a Root Bridge ID equal to it's own Bridge ID and a Sender Bridge ID that is its own Bridge ID. The purpose of the sender ID is to inform the other switches who is actually the sender of the BPDU message.

Each BPDU will be checked to see if it has a lower Root Bridge ID. If the BPDU is lower than the current switches BPDU, the current switch will then replace its own Root Bridge ID with the newly announced Root Bridge ID. If the Root Bridge ID is not lower then it will simply just forward the BPDU without making any changes.

As soon as the root bridge is determined, then configuration BPDU's will only be sent by the Root Bridge. The other switches must forward or relay the BPDU's while adding their own Sender Bridge ID to the message.

Bridge Protocol Data Unit - BPDU

2010-01-10T14:09:00.008-06:00

In order for Spanning-Tree to operate, Bridge Protocol Data Units (BPDU) are used to communicate between all switches. Switches must learn of other switches in the network. This is accomplished by each switch sending a BPDU frame out a port and using a unique MAC address of that particular port as the "source address". Given that the switch is unaware of other switches in the network, BPDU's are sent with a "destination address" of the STP multicast address 01-80-c2-00-00-00.

The 2 Types of BPDUs are:

Configuration BPDU
Topology Change Notification (TCN) BPDU

The 2 Goals of BPDU's are:

Elects reference points as the foundation for a stable spanning-tree topology.
Helps spanning-tree communicate topological changes to deal with loops and faults in the switched network.

Configuration BPDU are used to compute spanning-tree. It is how the switches in the network agree on which switch will be the root bridge. The BPDU's are pass amongst each switch every 2 seconds. Once the root bridge is determined spanning-tree uses BPDU's to communicate topological changes such as links going down and coming back up.

802.1d - Spanning Tree

2010-01-08T19:29:00.007-06:00

All Networks should be designed to primarily accomplish 2 things.

Efficiently transfer packets or frames.
Provide recoverability from faults in the Network.

To accomplish this goal, routing protocols are used in layer 3(routers). Layer 3 routing accomodates multiple paths to a network destination to be up and "active" while providing load sharing across those multiple paths.

In contrast, layer 2(switches) does not use routing protocols and active redundant paths. In fact active redundant paths are not allowed nor desirable. The question can be asked "How does layer 2 handle redundancy and fault tolerance". The answer is that Layer 2 uses Spanning-Tree (STP) for its network link redundancy. Spanning-Tree provides links redundancy so that a switched network can recover from faults without having to provide direct intervention from Network Engineers. STP is also known as IEEE 802.1d standard.

As Network Engineers we can use Spanning-Tree to avoid bridging loops. A bridging loop is when a single frame is forwarded back and forth between 2 switches. This endless loop of forwarding creates unbearable network congestion. These loops form because the layer 2 devices are unaware of each other.

Spanning-Tree (802.1d) was created to eliminate the possibility of bridging loops while using redundant swithches and swithch paths. Primarily STP (802.1d) enables all the switches to know of each other so they can negotiate a loop free network.

STP simply discovers all loops in the switched network and then shut downs redundant links before they are made available. STP informs switches when shut down links should be brought up in order to fix faults in the network. All connected switches will communicate via STP. Every switch will run the STP algorithm based on all the information that they receive from the neighboring switches. STP will create a root bridge and then calculate all redundant links to that root bridge. Once the redundant paths are known and calculated, STP will choose the best path with the least cost and then begin forwarding frame along that path. STP will disable and or block forwarding on all of the other redundant paths.

In summary STP creates communication between switches, discovers redundant paths, calculates best single path, blocks and or disables redundant paths, and enable blocked and or disable during network failure to maintain fault tolerance.

How to Reset Cisco Router Password

2009-10-12T18:28:00.006-05:00

The (>) prompt is for the ROM monitor mode. If you are having a problem interrupting the boot sequence of the router, you might be interested in this procedure to simulate break key sequence.
2. Now you should change the value of the configuration register in order to make the router neglect the contents of the NVRAM in the next boot up. This is achieved using the following command:
> o/r 0x2142
This command will change the sixth bit (originally the configuration register is 0x2102) to one. By doing so, the router will act as new in the next boot, i.e., the router will not look for the startup-config in the NVRAM.
3. Perform a restart to the router using the following command:
> i
The (i) stands for (initialize).
4. The router now will restart and ask you if you want to use the setup mode and of course you will say no. Now, in order not to loose the configuration that you already have in the router, you should go to the USER privileged mode and perform:
Router#copy start run
This will get you back your old configuration but with one exception, you already are in the privileged mode without having to know the password..!!!!
Now you put a new password or passwords if you may:
Router(config)#enable secret whateveryouwnt
And you can also put new console and telnet passwords if you like.
5. To get things going back to normal, change the value of the configuration register to its original form (0x2102) using the following global configuration command:
Router(config)#config-register 0x2102
6. Now you should save the configuration including the new passwords that you know:
Router#copy run start
7. Now reload and you are good to go:
Router#reload

How to Telnet Straight to Privilege Exec mode!

2009-10-09T13:22:00.005-05:00

You can telnet straight to the Privilege exec mode of a Cisco Router by doing the following:

click to enlarge

Command line interface configuration.

Type in "Config T"
Type in "Line vty 0 4"
Type in "Privilege level 15" >>>>there are different levels of access besides level 15
Type in "Password xyz" >>>>substitute xyz for whatever secure password you would like
Type in "Login"

Eight easy steps to Cisco ASA remote access setup

2009-10-07T17:19:00.001-05:00

There are eight basic steps in setting up remote access for users with the Cisco ASA.

Step 1. Configure an Identity Certificate
Step 2. Upload the SSL VPN Client Image to the ASA
Step 3. Enable AnyConnect VPN Access
Step 4. Create a Group Policy
Step 5. Configure Access List Bypass
Step 6. Create a Connection Profile and Tunnel Group
Step 7. Configure NAT Exemption
Step 8. Configure User Accounts

Step 1. Configure an Identity Certificate

Here I am creating a general purpose, self-signed, identity certificate named sslvpnkey and applying that certificate to the “outside” interface. You can purchase a certificate through a vendor such as Verisign, if you choose.

corpasa(config)#crypto key generate rsa label sslvpnkey

corpasa(config)#crypto ca trustpoint localtrust

corpasa(config-ca-trustpoint)#enrollment self

corpasa(config-ca-trustpoint)#fqdn sslvpn. mycompany.com

corpasa(config-ca-trustpoint)#subject-name CN=sslvpn.mycompany.com

corpasa(config-ca-trustpoint)#keypair sslvpnkey

corpasa(config-ca-trustpoint)#crypto ca enroll localtrust noconfirm

corpasa(config)# ssl trust-point localtrust outside

Step 2. Upload the SSL VPN Client Image to the ASA

You can obtain the client image at Cisco.com. As you choose which image to download to your tftp server, remember that you will need a separate image for each OS that your users have. After you select and download your client software, you can tftp it to your ASA.

asa(config)#copy tftp: flash:

Address or name of remote host [192.168.1.25]?

Source filename [anyconnect-win-2.3.2016-k9.pkg]?


Destination filename [anyconnect-win-2.3.2016-k9.pkg]?

Accessing tftp://192.168.1.25/anyconnect-win-2.3.2016-k9.pkg...!!!!!!!!

After the file has been uploaded to the ASA, configure this file to be used for webvpn sessions. Note that if you have more than one client, configure the most commonly used client to have the highest priority. In this case, we’re using only one client and giving it a priority of 1.

corpasa(config)#webvpn

corpasa(config-webvpn)#svc image disk0:/anyconnect-win-2.3.0254-k9.pkg 1

Step 3. Enable AnyConnect VPN Access

corpasa(config)#webvpn

corpasa(config-webvpn)#enable outside

corpasa(config-webvpn)#svc enable

Step 4. Create a Group Policy

Group Policies are used to specify the parameters that are applied to clients when they connect. In this case, we’ll create a group policy named SSLClient. The remote access clients will need to be assigned an IP address during login, so we’ll also set up a DHCP pool for them, but you could also use a DHCP server if you have one.

corpasa(config)#ip local pool SSLClientPool 192.168.100.1-192.168.100.50 mask 255.255.255.0

corpasa(config)#group-policy SSLCLient internal

corpasa(config)#group-policy SSLCLient attributes

corpasa(config-group-policy)#dns-server value 192.168.200.5

corpasa(config-group-policy)#vpn-tunnel-protocol svc

corpasa(config-group-policy)#default-domain value mysite.com

corpasa(config-group-policy)#address-pools value SSLClientPool

Step 5. Configure Access List ByPass

By using the sysopt connect command we tell the ASA to allow the SSL/IPsec clients to bypass the interface access lists.

corpasa(config)#sysopt connection permit-vpn

Step 6. Create a Connection Profile and Tunnel Group

As remote access clients connect to the ASA, they connect to a connection profile, which is also known as a tunnel group. We’ll use this tunnel group to define the specific connection parameters we want them to use. In our case, we’re configuring these remote access clients to use the Cisco AnyConnect SSL client, but you can also configure the tunnel groups to use IPsec, L2L, etc.

First, let’s create the tunnel group SSL Client:

corpasa(config)#tunnel-group SSLClient type remote-access

Next, we’ll assign the specific attributes:

corpasa(config)#tunnel-group SSLClient general-attributes

corpasa(config-tunnel-general)#default-group-policy SSLCLient

corpasa(config-tunnel-general)#tunnel-group SSLClient webvpn-attributes

corpasa(config-tunnel-webvpn)#group-alias MY_RA enable

corpasa(config-tunnel-webvpn)#webvpn

corpasa(config-webvpn)#tunnel-group-list enable

Note that the alias MY_RA is the group that your users will see when they are prompted for login authentication.

Step 7. Configure NAT Exemption

Now we need to tell the ASA not to NAT the traffic between the remote access clients and the internal network they will be accessing. First we’ll create an access list that defines the traffic, and then we’ll apply this list to the nat statement for our interface.

corpasa(config)#access-list no_nat extended permit

ip 192.168.200.0 255.255.255.0 192.168.100.0 255.255.255.0

corpasa(config)#nat (inside) 0 access-list no_nat

Step 8. Configure User Accounts

Now we’re ready for some user accounts. Here we’ll create a user and assign this user to our remote access vpn.

corpasa(config)#username hyde password l3tm3in

corpasa(config)#username hyde attributes

corpasa(config-username)#service-type remote-access

Finishing up

Don’t forget to save your configuration to memory.

corpasa#write memory

Verify your configuration by establishing a remote access session and use the following show command to view session details.

corpasa #show vpn-sessiondb svc

This guide should help you to get your remote access users up and running in no time. If you run into any difficulties, use the debug webvpn commands to diagnose the problem.

How to Configure ASA 5505 with ATT DSL

2009-10-07T15:18:00.002-05:00

Make sure that you connect the ethernet cable from your ATT router to the E0/0 port of the ASA 5505.

Get into global configuration mode and enter the following:

vpdn group ATT request dialout pppoe
vpdn group ATT localname xyz@att.net
vpdn group ATT ppp authentication pap
vpdn username xyz@att.net password *******
interface Vlan1
nameif inside
ip address x.x.x.x 255.255.255.0 >>> this is your clients ip default gateway to the internet
interface Vlan2
nameif outside
pppoe client vpdn group ATT
ip address pppoe setroute
interface Ethernet0/0
switchport access vlan 2
no shutdown
interface Ethernet0/1
no shutdown
interface Ethernet0/2
no shutdown
interface Ethernet0/3
no shutdown
interface Ethernet0/4
no shutdown
interface Ethernet0/5
no shutdown
interface Ethernet0/6
no shutdown
interface Ethernet0/7
no shutdown
exit
nat (inside) 1 0.0.0.0 0.0.0.0
global (outside) 1 interface
end
write

How to change the Remote Desktop listening port on Windows Vista!

2009-10-07T12:38:00.001-05:00

This will work with Sever 2003 and XP.

1.Open up the Windows Registry Editor and browse to this Registry path:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp2.Locate the PortNumber Registry key on the right-pane, double-click to open, click the Decimal option in the Base section, enter 443 in the text box and click OK (change 443 to the port number of your need).

Take note that:

The new TCP port for Remote Desktop service must not currently in used. To confirm the TCP port 443 is free or unused, type

netstat -an
find "443"

At the Command Prompt window. If there is no output from the netstat command, meaning that the TCP 443 port number is not in used (and thus available for new RDP listening port).

If you’re not comfortable with Windows Registry Editor, you can simply copy and paste the following Console Registry Tool command (Reg.exe) to an elevated Command Prompt window in Windows Vista:

You might need to download Reg.exe from Microsoft if it’s not currently in your Windows.
REG ADD "HKLM\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" /v PortNumber /t REG_DWORD /d 443 /f
To change back to the default, simply replace the PortNumber Registry key (in this case, TCP 443) to TCP port 3389.
How to restart Windows Remote Desktop service after changing its listening port?
There are at least two ways to enable/disable or restart Remote Desktop service – Group Policies or System Properties:
Using Group Policies (i.e. gpedit.msc)
1.Click the Vista Orb, type gpedit.msc in the Start Search text box (Vista Instant Search) and double-click the “gpedit” in the Program list
2.For Windows XP SP2:

In Computer Configuration, Administrative Templates, Windows Components, Terminal Services, double-click the Allows users to connect remotely using Terminal Services setting.
For Windows Vista Ultimate:
In Computer Configuration, Administrative Templates, Windows Components, Terminal Services, Terminal Server, Connections, double-click the Allows users to connect remotely using Terminal Services setting.
3.Click Disable to deactivate Remote Desktop and then click Enable to reactivate the service again.
Using System Properties dialog box

If the “Allows users to connect remotely using Terminal Services” Group Policy setting is set to “Not Configured”, the “Enable Remote Desktop on this computer” setting (on the Remote tab of the System Properties dialog box) takes precedence. Otherwise, the “Allows users to connect remotely using Terminal Services” Group Policy setting takes precedence.

How to Remove Unbuntu from a Dual Boot Vista System

2009-10-06T12:55:00.002-05:00

So how do you restore your MBR for Windows Vista?

1. Put the Windows Vista installation disc in the disc drive, and then start the computer.
2. Press a key when you are prompted.
3. Select a language, a time, a currency, a keyboard etc..., and then click Next.
4. Click Repair your computer.
5. Click the operating system that you want to repair, and then click Next.
6. In the System Recovery Options dialog box, click Command Prompt.
7. Type Bootrec.exe /FixMbr, and then press ENTER.
8. Reboot machine to verify Vista loading properly.
9. Reboot your machine with the Ubuntu CD and use the Ubuntu Partition Manager to remove the Ubuntu parition.

Unable to Launch ASDM Connection Timed Out Error!

2009-10-04T02:53:00.001-05:00

This is a very simple problem to fix. Simply log on to the ASA with via the console cable and follow the steps below.

Log into the ASA device via the console cable and go to global configuration mode
Type in "http server enable" - this turns on management.
Type in "http 192.168.1.0 255.255.255.0 inside" - subnet that you will allow management from.

How to Reinstall Cisco IOS from Rommon mode.

2009-09-27T10:23:00.001-05:00

You can reinstall any Cisco IOS from Rommon mode. Here are the commands that I used to load a new image from my TFTP server located at address 192.168.1.24.

You will notice that during the configuration that I entered the ip address of 192.168.1.2 to the router that I intended to load the image onto. Then I decided to give the router the ip address of 192.168.1.23. No biggie, I just re-entered the IP_ADDRESS=192.168.1.23

See the screen shot below.

click to enlarge

Steps to installing Cisco IOS image in Rommon mode:

Power off/on router and immediately send the cntl+break command.

At the the rommon 1 >: IP_ADDRESS=192.168.1.23

At the the rommon 2 >: IP_SUBNET_MASK=255.255.255.0

At the the rommon 3 >: DEFAULT_GATEWAY=192.168.1.254

At the the rommon 4 >: TFTP_SERVER=192.168.1.24

At the the rommon 5 >: TFTP_FILE=c2600-adventerprisek9-mz.124-15.T9.bin

At the the rommon 6 >: tftpdnld

Answer yes to proceed.

Troubleshooting Bus Error Crashes

2009-09-27T09:58:00.001-05:00

I ran across a strange issue after having rebooted my Cisco 2610 router. The router would just keeping rebooting and loading the image. I tried to reinstall various images from rommon mode but without success.

This is the error I was receiving.

click to enlarge

Troubleshooting Steps:

Power off router and send the ctrl+break command to enter rommon mode

Reinstall a new image from rommon mode since I can't boot into the router.

Problem still existed after various reinstallation of different ios images.

Reboot the router without any cards installed...in my case removed the NM-8A/S card.

Router rebooted without error.

Reseated the NM-8A/S card back into the slot and powered router back up.

Router booted up without error.

Conclusion:

If you are receiving bus errors then make sure that any newly installed memory modules or cards are first removed to see if the router will boot without them installed. If the router does reboot without them successfully then reseat the memory modules or cards and reboot the routers to determine if the problem is associated with those peripherals.

In my case, a simple reseating of the NM-8A/S card did the trick, but it very possible that some parts will have to be replaced in order to fix the problem.