Rancid monitors a router's (or device's) configuration, including software
and hardware (cards, serial numbers, etc), using CVS. Rancid currently
supports Bay routers, Cisco routers, Juniper routers, Catalyst switches,
Foundry switches, Redback NASs, ADC EZT3 muxes, MRTd (and thus likely IRRd),
Alteon switches, HP Procurve switches, Hitachi routers.

Rancid logs into each of the devices in a router table file, runs various
commands, chomps the output, and emails any differences from the previous
collection to a mail list.

A looking glass is also included with rancid, based on Ed Kern's in use on
http://nitrous.digex.net/. Rancid version has added functions, supports Cisco,
Juniper, and Foundry and uses the login scripts that come with rancid;
so it can use rsh, telnet, or ssh to connect to your router(s).