Console to Aux

Unanswered Question
Dec 2nd, 2008

Let's say I have two switches on two different floors of a building that have a trunked fiber connection. The one switch I have the console cable connected to a serial KVM where I can get in out of band and console to the switch, but because the fiber connection got severed I can't telnet to the other switch but I have to get into it. can I connect the Aux port from one switch to the console port of the other so I can telent in that way? or is there another way?


I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Giuseppe Larosa Tue, 12/02/2008 - 13:19

hello Mike,

unfortunately lan switches (modern ones at least) usually miss an aux port but the answer is yes a connection aux to console can be configured and the one with the aux acts as a terminal server providing access to the other device's console.

I did this successfully with routers.

have you alredy tried a shut/no shut cycle on the switch you can reach of the fiber link port ?

Hope to help


burleyman Tue, 12/02/2008 - 13:30

I want to set this up to avoid this problem. We had something simular happen so I wanted to see if this was possible. Can you send me how I have to have this configured? or direct me to some documentation.



Giuseppe Larosa Tue, 12/02/2008 - 21:43

Hello Mike,

first of all you need to identify the line number associated to the aux port:

RT-RM-TLD066-VPN-2#sh line | inc AUX

65 AUX 9600/9600 - - - - - 7 4397 0/1259 -


the number in my case is 65. This is useful to configure for reverse telnet

ip host new-vpn-2 2065 xx.xx.xx.253

the tcp port is 2000 + aux.linenumber

then you need to configure the aux port:

line aux 0

no exec

transport input all

transport output all

(I have also AAA authentication)

if I telnet to the host name I have to authenticate again and then I see the other router console

RT-RM-TLD066-VPN-2#sh users

Line User Host(s) Idle Location

65 aux 0 g.larosa incoming 00:02:04 new-vpn-2

66 vty 0 g.larosa new-vpn-2 00:02:05

* 67 vty 1 g.larosa idle 00:00:00

from a second vty 1, line 67 I can see that vty0 is connected to the host and to aux

To close it I usually use clear line vty.line.number from the second telnet session

you need a loopback on the router that acts as the terminal server: the masked address above is actually the ip address of a loopback.

Hope to help


burleyman Wed, 12/03/2008 - 05:51

I will try this out today...I hope :-)

I will post how this turns out.




This Discussion