Cisco IOS Cookbook, 2nd Edition

Storing Configuration Files Larger Than NVRAM

Problem

Your configuration file has become larger than the router’s available NVRAM.

Solution

You can compress your router’s configuration file before saving it to NVRAM to allow you to save more configuration information. The command service compress-config will compress the configuration information when the router saves the file, and uncompress it when it is required:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#service compress-config 
Router1(config)#end
Router1#

Discussion

Cisco generally ships its routers with more than enough NVRAM to store an average configuration file. However, there are times when configuration files exceed the available NVRAM. For instance, some routers contain large access-lists that could be hundreds of lines in length. Eventually, some configuration files will grow beyond the finite amount of NVRAM and you will begin to have problems.

The first sign of serious problems with an overly large configuration file is usually when the router refuses to save its configuration because of size. This is a dangerous problem because the router can no longer keep a copy of the whole running-configuration file in its NVRAM storage, and it is difficult to predict how much of your configuration will be lost if you were to reload the router.

Turning on compression roughly doubles the size of the configuration file you can store. You have to put the command service compress-config ...