It’s a fact of life that no matter how carefully you manage your equipment, something is bound to go wrong at some point. While Cisco has a great track record of providing stable equipment with a solid operating system, there are still times when something will go wrong. When problems do occur, fixes are usually issued by Cisco as an updated IOS release.
On a day-to-day basis, especially while studying, many of the problems that you will come across will be related to managing the IOS image and passwords. For example, it’s important to be familiar with how to gain access to a router when you’ve forgotten (or perhaps were never told) one of the required passwords. Along the same lines, you will need to know what to do in cases where your router’s IOS image is corrupted or missing.
Troubleshooting and password recovery of a Cisco router requires an understanding of the different working environments provided by the router, and how to reach them. In order to successfully access these environments, you’ll need to be familiar with what is known as the configuration register and how it impacts the operation of your router. Not only does this setting control how a router boots, but also the ability to issue break sequences, configure console port speeds, and so forth.
The topics that we’ll cover in this chapter include:
- The Cisco router boot process
- Router environments
- Understanding configuration register values
- Changing configuration register values from different environments
- Password recovery on Cisco routers
- Restoring missing or corrupted IOS images