NM-8A/S module as a terminal server

Using NM-16A/S or NM-32A/S is easy peasy, because they are dedicated terminal server modules and you have octal cables. But NM-8A/S is a bit more complex because you need more cables, adapters, and special commands to get this working. Now, I don’t recommend the NM-8A/S modules but sometimes you can get them really cheap compared to the other ones, so here’s how to set it up as a terminal server:

  • put the module into a 2621xm router (or any of the routers listed on nm-8A/S Cisco page)
  • take a Cisco CAB-232MT cable, connect it to one of the ports on the module
  • take the male end of the CAB-232MT cable and connect it to DB-25female>DB9male adapter.
  • connect the adapter to a standard cisco blue console cable
  • plug the rj45 into some other router’s console port

Now power up the 2621xm, go to the serial interface (remember that they’re numbered from the right):

conf t

int s1/0

physical-layer async


This causes the serial to go into async mode.

Now issue the command:

show line

This command shows you which line you need to use (in my case it was line 33, because the it’s S1/0 module. If it was S0/0 module, it would be line 1.)

Then, make a loopback0 interface and add an ip address to it:

int loop0

ip addr

Then, go to the line interface and modify the transport parameters:

conf t

line 33

transport input telnet

transport output telnet


Finally, create a host/port mapping:

ip host R1 2033

This maps the address/port to the name of the router that you want to manage.

Now you can manage other routers by telnetting to this router’s loopback interface:

telnet 2033

This moves you to the R1 console port.

Alternatively, just type R1 and press Enter.

You can use Shift+Ctrl+6 and then X to leave the managed router and go back to your terminal server.

Now add more mappings for other managed routers:

ip host R2 2034

ip host R3 2035

ip host R4 2036

and so on and so forth.


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