Understanding the network.pdf - Back to Home

If you use AAA instead of local authentication, there is no need to
specify an authentication method. By default, the port will use the
globally defined authentication method for login.
Disaster Recovery
The routers are up, everything is great, and BANG!—disaster strikes.
The enable password is lost, or a power surge zapped the router and
the IOS image is corrupted. It doesn't matter how it happened. You
just need to get the router back online, and to do that you need it up,
and you need access.
Setting the Bootstrap Behavior
A Cisco router's bootstrap behavior is set using what is known as the
configuration register (conf-reg). On the early Cisco routers (such as
AGS), the conf-reg was set with jumpers on the router's system
board. On the later Cisco models (Cisco 1000 and up), the conf-reg
can be set in global configuration mode using the config-register
command:
Router# configure terminal
Router(config)#config-register 0x2102
Router(config)#^Z
Router#
Alternatively, if access to global configuration mode is unavailable,
the ROM Monitor (rommon), which is similar in function to a PC's BIOS
mode, can be used. To access rommon, you need to be attached to the
console port and you need to issue a terminal break sequence through
your terminal emulator software. Check your package's
documentation for the correct key sequence; C-Kermit's break key is
Alt+B. In most cases, break is disabled once the router is up and
running. So the easiest way to get into rommon is to power-cycle the