Managing the Configuration Register
All Cisco routers have a 16-bit software register that’s written into NVRAM. By default, the
configuration register
is set to load the Cisco IOS from
flash memory
and to look for and load
the startup-config file from NVRAM.
Checking the Current Configuration Register Value
You can see the current value of the configuration register by using the
show version
command
(
sh version
or
show ver
for short), as demonstrated in Table 2.2:
The only way to view the configuration register is through the show version command:
Router#
sh version
Cisco IOS Software, 2800 Software (C2800NM-ADVSECURITYK9-M),Version 12.4(12),
RELEASE SOFTWARE (fc1)
[output cut]
Configuration register is 0x2102
The last information given from this command is the value of the configuration register. In
this example, the value is 0x2102, which is the default setting. The configuration register
setting of 0x2102 tells the router to look in NVRAM for the boot sequence.