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!