Configuring A Cisco 2600 Series Router as a Terminal Server

I have a small lab I put together to help bash around new ideas, it consists of:

  • 2 Cisco 2611s
  • 2 Cisco 3500 XLs

Recently I've been jumping between devices using a single console cable... and that got old pretty quick. I was able to pickup a NM-16A Async module which provides 16 more lines to my 2600. To use this card I also needed a Cisco octal cable. cisco-nm-async-16cab_oct_async Steps: 1) After inserting the card and screwing in the octal cable you can verify that there is added line capacity: Router_A#show version | i line 16 terminal line(s) 2) Before you proceed you will need to find out what line numbers your new NM-16A uses, in my case it was 33-48: Router_A#show line Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int * 0 CTY - - - - - 6 0 0/0 - 33 TTY 9600/9600 - - - - - 2 1 35/106 - 34 TTY 9600/9600 - - - - - 4 19 0/0 - 35 TTY 9600/9600 - - - - - 0 0 0/0 - 36 TTY 9600/9600 - - - - - 0 0 0/0 - 37 TTY 9600/9600 - - - - - 0 0 0/0 - 38 TTY 9600/9600 - - - - - 0 0 0/0 - 39 TTY 9600/9600 - - - - - 0 0 0/0 - 40 TTY 9600/9600 - - - - - 0 0 0/0 - 41 TTY 9600/9600 - - - - - 0 0 0/0 - 42 TTY 9600/9600 - - - - - 0 0 0/0 - 43 TTY 9600/9600 - - - - - 0 0 0/0 - 44 TTY 9600/9600 - - - - - 0 0 0/0 - 45 TTY 9600/9600 - - - - - 0 0 0/0 - 46 TTY 9600/9600 - - - - - 0 0 0/0 - 47 TTY 9600/9600 - - - - - 0 0 0/0 - 48 TTY 9600/9600 - - - - - 0 0 0/0 - 65 AUX 9600/9600 - - - - - 0 0 0/0 - 3) You need to create a loopback to be used to telnet to each of the lines: interface Loopback0 ip address 126.0.0.1 255.255.255.255 no ip redirects end 4) Next you need to configure the lines of this card with your preferred settings: line 33 48 no flush-at-activation transport preferred telnet transport input all stopbits 1 flowcontrol hardware 5) Finally, it's nice to add ip hosts on the router for ease of use. Note that the tcp port number for our new lines are named with 20xx where "xx" is the actual line number. For example, our first line is "33" so you need to connect to port "2033." After this is done plug the rollover cable coming from the octal cable labeled "1" into the console port of the device you want to manage. In my scenario, cable "1" == line 33 == port 2033, cable "2" == line 34 == port 2034, etc... ip host r2 2033 126.0.0.1 ip host s1 2034 126.0.0.1 You should now have a console server in which you can "reverse" telnet into other devices connected through the octal cable. You should be able to issue commands such as "telnet r2" and be dropped into a console session. To return to the router press "control + shift + 6 +x." To disconnect the session type "disconnect <connection number>" or "disconnect <hostname> ." Here is the relevant configuration parameters: ip host r2 2033 126.0.0.1 ip host s1 2034 126.0.0.1 interface Loopback0 ip address 126.0.0.1 255.255.255.255 no ip redirects line 33 48 exec-timeout 0 0 no flush-at-activation logging synchronous no exec notify transport preferred telnet transport input all stopbits 1 flowcontrol hardware A big thank you to Gerry Murray for initial guidance and introducing me to this.

Tagged as cisco , console console server , octo cable
Written by Andrew Konkol on December 7th, 2009

1 Comments

Thanks for sharing this set of instructions. Really informative.

Sally S.
April 15, 2011
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