It might happen on your CCNA exam, it might happen on your production network - but sooner or later, you're going to have to perform password recovery on a Cisco router or switch. This involves manipulating the router's configuration register, and that is enough to make some CCNA candidates and network administrators really nervous!
It's true that setting the configuration register to the wrong value can damage the router, but if you do the proper research before starting the password recovery process, you'll be fine.
Despite what some books say, there is no "one size fits all" approach to Cisco password recovery. What works on a 2500 router may not work on other routers and switches. There is a great master Cisco document out on the Web that you should bookmark today. Just put "cisco password recovery" in your favorite search engine and you should find it quickly.
The following procedure describes the process in recovering from a lost password on a Cisco 2500 router. As always, don't practice this at home. It is a good idea to get some practice with this technique in your CCNA / CCNP home lab, though!
The password recovery method examined here is for 2500 routers.
An engineer who finds themselves locked out of a router can view and change the password by changing the configuration register.
The router must first be rebooted and a