Something commonly overlooked is how to store incremental backups of your Cisco router configurations. Some people use Rancid or Kiwi Cat Tools and they are great, but what most people do not realize is IOS 12.3(4)T and higher has an archive command. Each time you perform a write mem or copy run start the router will save an archived version to the path you specify.
In this example, we chose to save the archive configuration files on the flash card in slot0; however, you can also store the configuration files remotely using such protocols as TFTP.
To create an archive of old configuration files, use the following set of commands:
Router1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#archive
Router1(config-archive)#path slot0:/configs/$h
Router1(config-archive)#write-memory
Router1(config-archive)#time-period 1440
Router1(config-archive)#end
Router1#