The Configuration Register

By: Chris Bryant

Bottom line: To earn your Cisco CCNA and CCENT certifications, you've got to understand the configuration register on Cisco routers and switches. This is also a great practical skill to have, because one day you will have to change the config register, most likely to perform a password recovery.?

I will just give this warning one time: If you change the register to an incorrect value and then reload the router, you can cripple the router and even Cisco can't bring it back.

No pressure, right?? :)

You really just have to be careful and get the right value for what you're trying to do before you change the config register.? Another key is to change the register back to the original value once you're done with your work.

To see the current config register value, run the always-helpful command show version.? The config register value is at the very bottom of that output, but while we're here, let's take a look at all of this information.

Router1#show version

Cisco Internetwork Operating System Software

IOS (tm) 2500 Software (C2500-I-L), Version 12.1(20), RELEASE SOFTWARE (fc2)

Networking
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