Router Basics: The Lost Configuration

In this video, Tony Fortunato explains how a router can lose its configuration when rebooted.

Tony Fortunato

September 7, 2016

1 Min Read
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I was inspired to put together videos that covered basic networking skills last year, while working with an install team as a lead technician. Everyone on the team had a different  level of experience, which is always a challenge.

For example, when I asked someone to retrieve a backup router and reconfigure it, I was told that there something "weird" with the replacement router. When I asked what was wrong, the admins explained that even though they configured the router, the router was ignoring it. I understood right away what the problem was; it's a common one that can trip up inexperienced IT admins. When a router is rebooted or loses power, it can lose the configuration you set. In this video, I demonstrate the problem.

I explained to the install team that some people set the configuration registry to ignore the configuration when storing equipment. Using the show version command, I showed them that the registry was set for 0x2142, which tells the router to ignore the startup configuration. I then used the show startup-config command to prove that the configuration was indeed there. I revealed that the solution is to write config-register 0x2102.

When we reloaded the router, the configuration was no longer ignored. Cisco explains this issue in more detail in a troubleshooting tip. 

I always try to figure out if equipment I use is susceptible to this problem in case I ever run into it.

As an aside, when it comes to getting familiar with configuration commands in a Cisco environment, you don’t even need to have the physical equipment.  You can use Cisco’s Packet Tracer software to run tests on a simulated network without fearing that you may mess something up.

About the Author(s)

Tony Fortunato

Sr Network Performance Specialist

Tony Fortunato is a network performance expert who has been designing, implementing and troubleshooting networks since 1989. His company, The Technology Firm, provides clients of all sizes with services ranging from project management, network design, consulting, troubleshooting, designing custom-designed training courses, and assisting with equipment installation. Tony's experience in networking started with financial trading floor networks and ISPs, where he learned to integrate and support equipment from various vendors. Tony has taught and presented at numerous colleges and universities, public forums and private classes. He blogs frequently at NetworkDataPediaand has a popular YouTube channel.

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