recovery can be performed. First, software called the ROM monitor (rommon) is held in ROM
on all routers and actually provides the code that is first used to boot each router. rommon has
a rudimentary command structure that is used as part of the password recovery process. A
limited-function IOS is also held in either ROM or in additional Flash memory called bootflash;
in either case, the IOS in bootflash or ROM is used mainly in cases where the IOS in flash is
not available for some reason. Finally, bit 6 of the configuration register set to binary 1 means
that the router should ignore the NVRAM configuration when booting.
NVRAM configuration file. The router will be up, but with a default configuration; this enables
a console user to log in, enter privileged mode, and change any encrypted passwords or view
any unencrypted passwords. To cause the router to ignore NVRAM at boot time, the
configuration register must be changed. To do that, you must be in privileged mode--and if you
were already there, you could reset any encrypted passwords or view any unencrypted ones.
It seems to be a viscious circle.
configuration register and that a console user can get into rommon mode by pressing the Break
key during the first 60 seconds after power-on of the router. Knowing how to reset the config
register enables you to boot the router (ignoring NVRAM), allowing the console user to see or
change the unencrypted or encrypted passwords, respectively.
identical. Table 2-7 outlines the process for each type of router.
2600, 3600, 4500, 7200,
7500
2500, 3000, 4000, 7000
on again.
the first 60 seconds.
console devices keyboard.
register so that bit 6 is 1.
confreg, and answer the
prompts.
o/r 0x2142.
an IOS.
command or, if unavailable,
power off and on.
initialize.
which will be prompted for
at console.