Starting up, plugging in

All Cisco's that I've worked with have a Console and an Aux port. On the bigger routers these are DB25 ports (one male, one female) and on smaller routers (2500's, 3600's) they are RJ45 jacks. The router should come with a kit containing a black cross-over console cable, and two RJ45<->DB25 convertors (one male, one female) and a RJ45<->DB9 convertor so that you can pretty much plug a console into any terminal. The pinouts should be documented in a little hardware guide book that comes with the routers. The black RJ45 cable is a cross over cable and cannot be used for ethernet. If it doesn't work for you, try using a straight through (as a crossover cable is the equivalent of a null-modem).

Cisco RJ-45 to DB-25 pin-outs and cable creation

Cisco RJ-45 to DE-9 pin-outs and cable creation

The cisco documentation notes that the console serial settings should be 9600,n,8,2 however I've always justed 9600,n,8,1

When you boot up for the first time the cisco should walk you through an initial configuration dialog in which you can setup some IP addresses. Generally I say no to pretty much everything, and just do it by hand. The default is to enable IGRP which I don't recommend unless you actually need it (most people don't).
If your router already has a configuration and you want to clear it and start fresh, go into enable mode and type write erase and then reload the router without saving the configuration.

Cisco's in general have two modes, normal user mode, and enable mode. To toggle between them you use the commands enable and disable and generally the prompt will change from hostname> to hostname# when going into enable mode.

Modern cisco's have a variety of passwords; there's the enable secret which is the password used to go into enable mode. There's also an 'enable password' which is used to go into enable mode when the encryption software is not running (this is rarely or never - I always use 'dummy' as the 'enable password'). There's a 'vty' password which is the password used when you telnet to the router, and there are also passwords for the console port and the aux port. Not all passwords are required, I normally only configure a vty password and an enable secret.

If for some reason you lose your enable password, login to the router and do a show version. Near the bottom of the output you will see something like:

Configuration register is XXXX

0x2102 is a typical value. Then power cycle the router, and immediately after it shows the bootup banner, send a BREAK to the console. You should be dropped to a '>' prompt. At this prompt do the following:

> o/r
> i

and the router will then boot. When it comes up, it will not parse the configuration file, and you should be able to go into enable mode and set a new password. A word of caution: you will lose all non-trivial configuration such as dynamic routing, frame-relay, isdn - pretty much everything except static routes and interface IP addresses. Once you've reset the enable secret (and/or enable password) then issue:

router#config term
Enter configuration commands, one per line.  End with CNTL/Z.
router(config)#config XXXX
router(config)#^Z
router#

where XXXX is the value shown in the show version - if you were unable to login to view that value, try using 0x2102

Last Updated: Fri Oct 2 14:09:54 PDT 1998

This is part of Nik's website - email me with questions or comments at nikm@cyberflunk.com.