Comparing Config Differences

When I started as a network engineer, whenever I configured something and forgot what it was, I usually do "show start" and "show run" to compare the difference manually before I do a "write mem". Believe me, it was an eyesore comparing the start-up and running-config line by line. There is a easy way though to compare the configs and the command is "show archive config differences" for the router to compare the start-up and the running-config. Check the output below.

Router#show archive config differences
Contextual Config Diffs:
+no aaa new-model
interface FastEthernet0/0
+description to LAN
+ip ospf cost 100
+duplex half
+mpls ip
-aaa new-model
-aaa session-id common
interface FastEthernet0/0
-description to Building 2
-ip ospf cost 800
-duplex full

The commands prepended with a "+" means that this commands are in the "start-up config". The ones with "-" are in the running config. Of course when you do a "write mem" after this and you issue the command, you won't be seing any differences :). Good day!


5 Responses to "Comparing Config Differences"

Anonymous said... January 13, 2012 at 3:23 PM


Unknown said... March 1, 2013 at 1:49 PM

Thank you. I didn't know this. Really useful.

yannick said... March 10, 2013 at 1:25 AM

thanks, this will definitely help me

Unknown said... October 29, 2013 at 1:44 AM

thanks! never knew this existed.

vineet said... April 25, 2014 at 12:13 PM

its awesome

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The Dreamer

A fun loving person who enjoys learning new things. Currently working as a Network Engineer supporting the global network of a Fortune 500 company. This blog serves as my notes for the labs I created for my CCIE journey. I can guarantee there are errors in my posts. If you spot them, please let me know.

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