Friday, 3 February 2012

Cold or Warm Reboot/Reloads on Cisco routers

Unbenown to me, you can warm reload Cisco routers and cut down the boot time.  I read this on Jermey Gaddis' blog from the states.  The guy knows his stuff, but on with the learning...

Have a go:

Conf t

Yes thats it.  You can configure other variables such as allowing the router to warm reboot a few times and when at a certain limit perform a cold restart etc, but the basic command is above.  I'm sure you know how to use the tab and question marks on your keyboard by now...

To then reload the router/switch from the prompt type 'reload warm'.

Obviously there are pro's and con's to this command.  The boot time is reduced, but you need a bit of room in RAM in order to buffer the command. 
The router simply saves the state in RAM and boots from that, rather than all the copying/decompressing the IOS image from flash each time.  I suppose if your IOS is corrupt (er... not sure how many times/if ever I've heard of this) in your running-config, then a cold restart will load a fresh IOS image back on.  But.. lets be realistic, we want quicker booting routers, so this should be a staple command.

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