Chapter 10 began with a look at the boot process of a Cisco router, including an overview of the different environments into which a Cisco router can be booted – ROM Monitor mode, the boot image stored in ROM, or a normal IOS image stored in Flash memory or on a TFTP server. The break […]

There may also come a time where you router doesn’t have a valid IOS image in Flash memory - perhaps because you have accidentally erased Flash, upgraded your router’s Flash memory, or the image contained in Flash has become corrupted. This leaves you with a couple of options, one of which is to use ROM […]

If one thing is for certain, it’s that at some point you’ll forget the password that you assigned to a router, or be asked to configure a router whose password you cannot be provided with. The good news is that with physical access to the console port, you’re in luck. Now that you know about […]

Now that you understand a little more about configuration register settings, let’s take a look at how current register settings can be identified, and then changed.
The easiest way to determine a router’s current configuration register setting is by using the show version command. The configuration register setting will appear at the end of the command’s […]

When it comes time to troubleshoot or initiate password recovery procedures on a router, one element that you’ll definitely need to be familiar with is the software configuration register. The configuration register is a 16-bit number, represented in hexadecimal, which controls everything from the way in which a router boots to whether or not it […]

By default, a Cisco router uses a configuration register setting that tells it to boot using the first IOS image stored in Flash memory. If a valid IOS image isn’t found in Flash, it will then attempt to “netboot” using an IOS image stored on a TFTP server. If even this fails, the default configuration […]

Recall from Chapter 6 that the read-only memory (ROM) on a Cisco router also includes a limited IOS version that can be used to boot the router in cases where an IOS image is not present. This limited IOS version is commonly referred to as the boot image (or RxBoot) and provides an environment from […]

As its name suggests, ROM Monitor is stored in ROM and is implemented in firmware. ROM Monitor mode is actually the bootstrap program that we talked about in previous chapters. The bootstrap program is responsible for initializing hardware and loading the Cisco IOS. As such, it is the first thing loaded by the router at […]

Way back in Chapter 6, we took an introductory look at how a Cisco router boots by default, according to factory-configured settings. However, you will also need to know how to alter settings such that a router can boot into different environments, if necessary. For example, if a router password is lost or misplaced and […]

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 […]