October 20, 2009

Cisco IOS - getting out of trouble

As simple as this tip is, you will be amazed on how often it is overlooked during remote night maintenance work. I have therefore decided for that reason to post it here.

So, you are sitting at home, editing an IOS configuration of X router during a maintenance window. Your only available remote login is through the wan interface. A bad access list and you can be locked out of the router till you physically go to the office to undo the changes.

It is late and you don’t fancy driving!

Here is a small tip which could save you the hassle

Prior to editing

edge1#reload in 10

Reload scheduled in 10 minutes

Proceed with reload? [confirm]y

Now as you guessed, you just issued the routerĀ  to reboot in 10 minutes

Now start editing…

When done, if all is good and all is working as expected, you can then proceed to cancel the scheduled reboot

edge1#reload cancel

The scheduled reboot is now cleared… if you happened to lock yourself out of the router, within the 10mn lapse time from the moment you issued the reload command, the router would reboot with the startup-config and give you access back to your router (assuming of course you didn’t save your running-config changes).

I hope that was informative!