Wednesday, 5 August 2009

Reverse Telnet - Using an AUX port to Console in

Hi again, just a quick note this time on "Reverse Telnet".

The reason behind this, is that I have seen several incorrect or incomplete articles out there and none seem to really detail how it is done.

1) The cable
Has to be an Rollover Cable with RJ 45 at both ends like this:

2) From the router you wish to remote from (i.e. the router whose AUX port you are using)
Configure the AUX port like so:

line aux 0
modem InOut
transport preferred all
transport input all
transport output all

3) Configure your loopback 0 with an ip address

interface Loopback0
ip address

4)Work out the Line Number of your Aux port and add 2000 to it:

Tty Typ Tx/Rx A Modem
0 CTY - -
* 65 AUX 9600/9600 - inout
* 66 VTY - -
67 VTY - -
68 VTY - -
69 VTY - -
70 VTY - -

5) If you see a '*' you need to clear it.

clear line 65

6) Telnet in:

telnet 2065

Remember that 2065 is 2000 + the line number (65)

7) To disconnect the connect hold down "Ctrl+Shift+6+x"

Some say use a straight through cable (never worked for me)
Some say use "speed 19200" however this does not work in all circumstances, "speed 9600" works better for me.
If you get "connection refused" when trying to telnet in use "clear line #" to fix it
Once connected to clear the connect hold down "Ctrl+Shift+6+x"

Just tested in the lab between 2610XM and 2610 and other than clearing the line it works perfectly :)


Child Abuse/Molestation said...
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Child Abuse/Molestation said...
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Technology at its best and worst said...

If I wanted to download an IOS version from one router to the other, could this be done via this connection? If so, how?

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