Reverse telnet from a Portmaster 3 to a Cisco console port

We have a remote POP that consists of a Cisco 2600 router, and a Lucent Portmaster 3

Normally to make any configuration changes to the remote pop, we would just telnet in and do the changes.

However we needed some sort of backup method that would allow us to get access to the Cisco in case we ever made a "wrong" change and stuffed up the routing etc thus preventing telnet access.

We chose to hook the console port of the PM3 to the Console port of the Cisco.

So in the event of a routing problem, we could dial into the PM3 and then open a reverse telnet session to the Cisco via this console cable.

The reverse telnet session would give us normal access to the cisco to allow us to fix whatever mistake we just made in the routing config.

Heres the steps we followed :

Setup hardcoded username/password on cisco for console port

aaa authentication login STORE_LOCAL local
username conun password conpw
line con 0
location ** CONSOLE CABLE
speed 115200
exec-timeout 0 0
login authentication STORE_LOCAL
transport input none
flow-control hardware

Make sure dip switch 1 is down on back of portmaster

Wire up the cable.

The cable we used is the blue console cable and DB9 adapter that ships with cisco routers. Plus we had to use a 9-25 pin adapter to make the cable fit the pm3 console port. Heres what the final cable looks like

[cisco console port]--[blue RJ45 cisco cable]--[cisco RJ45-DB9F adapter]--[9pinM 25pinM adapt]--[Pm3 C0 port]

Configure the c0 port on the pm3

PM3> set c0 speed 1 115200 
PM3> set c0 speed 2 115200
PM3> set c0 speed 3 115200
PM3> set c0 xon off 
PM3> set c0 over xon off 
PM3> set c0 rts on 
PM3> set c0 device /dev/network 
PM3> set c0 service_device telnet 6000
PM3> set c0 modem off 
PM3> reset c0 

make sure pm3 is configured to allow !root login via serial

PM3> set serial-admin on

If the PM3 ethernet address cannot be reached via the internet :

dial into the portmaster with a modem login as !root

Open a reverse telnet session to the C0 port

telnet 6000

Cisco login prompt should appear

username is conun
password is conpw

Then you should have access to the the Cisco's command prompt!