Hi Vishal,
The router could be rebooting continuously due to any of the several reasons. It may be crashing, the reason for which can be found out by checking the crashinfo files. It could be due to some mismatch in the IOS requirements and the available memory resources. However, to troubleshoot it, we need to first get the router booted up properly. Here the are steps you can follow to achieve that :
- Keep tapping 'ctrl' + 'Pause\Break' key while the router is booting up, so that the router will boot up in ROMMON mode.
- Once in ROMMON mode, type the 'confreg 0x2142' command. This will set the value of configuration register on the router to ignore 'NVRAM' while booting up.
- Then issue the 'reset' command to reboot the router.
- This time, the router will bootup without loading the 'startup config'.
- It will ask if you wish to enter the 'initial configuration dialog box' ...type 'no' and press enter.
- Next, enter privilege mode and copy the startup config over running config using 'copy start run'. <- Make sure you don't type it the other way round or you'll lose your configuration permanently.
- Next, change the value of config register back to default using the global mode command 'config-register 0x2102'.
- Save the config using 'write memory'.
Now, we have successfully booted-up the router and can start looking for the reason behind the continuous restart issue.
Check for the memory requirements of the IOS installed on the router (can be checked at IOS download page at Cisco.com) and make sure you've enough memory on the device.
You can also check the flash to see if there are any crashinfo files, using "dir flash:" command.
Regards,
Pawan
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