On more than one occasion I have needed to access the console port of a switch, but I wasn’t physically there but I did have a router near the unit. You can easily setup your router to act as a Terminal server, allowing you to use a flat rolled cable between the Router’s AUX port and the switch’s CONSOLE port. First you need to properly configure your AUX port:
line aux 0
modem InOut
transport input all
stopbits 1
flowcontrol hardware
Now in order to use this feature, log into your router and do the following:
- from the command prompt enter: SHOW LINE
- Find the line number for AUX (in this example it is Line 5)
- Telnet to the IP address of the router you are logged into, but when you telnet you will need to indicate a specific port. That port is 2000 + the line number. So in this example your command would look like this: ‘telnet 172.17.10.1 2005′
- This will get you access to the remote device
- When you are finished with the session on the remote device break out with CTRL+ALT+6, followed by x one second later. If you by chance use SecureCRT for your Telnet sessions you can setup a key map that sends the following ASCII standard for that command ‘\036\px’. You can read more about this on VanDyke’s SecureCRT Forum.
- Once you are back in the original device you can return to the remote device by simply pressing the ENTER key.
- If you are finished with your remote session, you can issue a CLEAR command to close that connection. In this example the command would be ‘CLEAR LINE 5′
I always need to look up features on different Cisco routers and switches. Cisco actually produces two documents that let you quickly see all the available models and associated features:
Cisco Router Guide
Cisco Catalyst Switch Guide
Sometimes you need a quick and easy way to test a T1 connection on a piece of equipment. For example, you want to make sure that the T1 WIC on your router is working.
To construct a loopback plug, simply take a single RJ45 plug and connect pin 1 to 4 and pin 2 to 5.
In setting up my home lab, one thing that I needed to do was communicate between my routers using the T1 WICs. For the physical cable connection it is necessary to use a T1 Crossover cable. This is really simple to construct. Using standard twisted pair cable and RJ45 ends, make the following connections: pin 1 to 4, 2 to 5, 4 to 1 and 5 to 2. Below is a diagram:
I have a couple of routers as part of my home lab that I am using for my Cisco certification studies. One thing that I wanted to do was connect two routers together via their T1 WICs. There are two things you need to do:
- create a T1 crossover to connect the routers
- set the clock settings on each routers’ serial interface to simulate the T1
In another post I will put the details of making a T1 crossover cable, here is a simple example of the configuration you need to apply to each routers’ T1 serial interface.
**apply this to router #1**
ip address 192.168.1.1 255.255.255.248
encapsulation ppp
fair-queue
service-module t1 clock source internal
service-module t1 timeslots 1-24 speed 64
service-module t1 framing esf
service-module t1 linecode b8zs
no shut
**apply this to router #2**
ip address 192.168.1.2 255.255.255.248
encapsulation ppp
fair-queue
service-module t1 clock source internal
service-module t1 timeslots 1-24 speed 64
service-module t1 framing esf
service-module t1 linecode b8zs
no shut
Have you ever needed to quickly find out which switch port a network device is plugged into and you only know the IP address of the device? You could always trace the cables in your data closet and drive yourself crazy or you could use a few simple commands on your switch and quickly find it.
sh ip arp | inc <ip address>
This will return the mac address
sh mac-address-table | inc <mac address>
This will return the switch port
If the IP address is on another switch, the port that is returned in the output will be for the trunked port that goes to the next “hop”. Go to the next switch and repeat.
sh run int <switch port>
This will return the config for that interface
Here is an example:
switch01#sh ip arp | inc 172.16.11.200
Internet 172.16.11.200 0 0080.a38a.10dc ARPA Vlan11
switch01#sh mac-address-table | inc 0080.a38a.10dc
11 0080.a38a.10dc dynamic ip GigabitEthernet3/3
switch01#sh run int gi3/3
Building configuration…
Current configuration : 152 bytes
!
interface GigabitEthernet3/3
description IBM APPLICATION SERVER
switchport access vlan 11
switchport mode access
qos trust dscp
spanning-tree portfast
end
switch01#
I know there are a ton of Cisco networking websites out there, so I figured why not start another. The real reason for this site is so I can have a place to store my thoughts, notes and bookmarks as I start my journey toward Cisco certification.