Where does the router fallback to load IOS when the IOS in flash memory is corrupted?

[kkanur]

If the ios image stored in flash is corrupted from where does the IOS is picked up?

[InayathUlla Sharieff · Accepted solution]

Hi,

The following details the router boot process:
1. The router is powered on.
2. The bootstrap program (ROMmon) in ROM runs Power-On Self Test (POST)
3. The bootstrap checks the Configuration Register value to specify where to load the IOS. By default (the default value of Configuration Register is 2102, in hexadecimal), the router first looks for “boot system” commands in startup-config file. If it finds these commands, it will run boot system commands in order they appear in startup-config to locate the IOS. If not, the IOS image is loaded from Flash . If the IOS is not found in Flash, the bootstrap can try to load the IOS from TFTP server or from ROM (mini-IOS).

Last if it doesnt find the software anywere it would end up in rommon mode.

HTH

Regards

Inayath

[kkanur]

Thanks Inayath for the explanation :)