How to Compare Startup and Running Config : Difference

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When managing Cisco IOS network devices, administrators do come across occasions when they forget what recently they configured and then starts the tedious activity of comparing “show startup-config” and “show running-config”.

The comparison activity is not only tiring but also may take a long time to resolve.

Let’s say a situation where only 1 hour of downtime is given by Business to perform a small change on Cisco device and at least 30 minutes of critical time is utilized by administrator in comparing and finding what the changes were performed.

Alas … indeed a nightmare.

So here is the command which can address the comparison vows –

“Show archive config differences”.

Below is example where the command is given and out is as below –

R1#show archive config difference
Contextual Config Diffs:
interface FastEthernet0/1
+no ip address
+shutdown
interface FastEthernet0/1
-ip address 192.168.12.1 255.255.255.0
-router eigrp 1
-network 192.168.12.1 0.0.0.0
-no auto-summary

Note – In the above output, “+” sign refers to configuration present in “startup-config” while “–“sign is for configuration part of “running configuration”.

And Of course, when we do a “write memory” after this and issue the command, no difference will be seen.