Easy to do.. just use the AUX port (BTW, this can be done using any Cisco IOS router that has an AUX port). For the 1811, I suggest the following (this is how I normally do it):
! presume you have aaa new-model configured
aaa new-model
! suggest making a "none" type of method for login
aaa authentication login my-none none
! configure the aux port
line aux 0
! this is just a sanity setting to force a port release every 60 mins. remove this if you want long lived
! terminal server sessions, or adjust as needed
session-timeout 3600
! this will prevent the 1811 itself from soliciting a login on the reverse telnet session. if you want the 1811
! to enforce a login (aka if you want to protect the attached device via an 1811 based login sequence),
! then adjust this to a different aaa login method. In my case, I enforce login on the attached serial device
! and find having the IOS 1811 doing a login to be a nusiance.
login authentication my-none
! subtle but important step here.. turn off the aux line "exec" processing. if you do not do this, it will still work
! but when you connect, do not be surprised to find a ton of junk coming out... as if the exec is on, the anytime
! the attached device output.. aka inputs to the aux.. then the "exec" will try to process it like an IOS CLI command.
no exec
! at minimum, one has to allow telnet (as that is really the only thing that can attach via reverse telnet)
transport input telnet
! adjust this if needed, note 9600 baud is the default so it will not show up
speed 9600
Also suggest the following:
! putting this at the top of the global config will help prevent "hung" sessions. basically if
! someone abruptly disconnects, within 5 mins the reverse-telnet session will be released on the
! 1811. aka, prevents one from having to do tedious "clear line" on the 1811 for a hung reverse-telnet
service tcp-keepalives-in
Once you have this in place.. do a "show line"
1811#show line
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
0 CTY - - - - - 0 0 0/0 -
1 TTY - inout - - - 0 0 0/0 -
5 AUX 9600/9600 - - - - - 3 0 0/0 -
The AUX port should be line "5" on an 1811. As such, the reverse-telnet port to use for this port is "2005" (aka 2000 + line#). Thus do a telnet to your 1811, but change the TCP port from 23 to 2005.
QED.
~G
the
