Contextual Configuration Diff Utility is the official Cisco name for what Linux people call diff. Diff in it's most basic form takes two text files and tells you what is different between the two files line by line. Before we look at IOS let's take a basic example of diff from a Linux box.
Listing of File1.txt
applesListing of File2.txt
applesExample of diff
storyb@nettools:~$ diff file1.txt file2.txt 3c3 < coffee --- > cottage cheese 5c5 < eclairs --- > fudge
In this example, you can see that it shows that coffee was in the first file, but cottage cheese was in the second and likewise that on line 5 eclairs was in the first file, but fudge was in the second.
Cisco's diff works very similarly to Linux's. In the following example of using IOS' diff we will use the following two abbreviated IOS configuration files.
Listing of iosconfig1.cfg
Listing of iosconfig2.cfg
no ip subnet-zero ip routing router ospf 1 network 192.168.1.0 0.0.0.255 area 0 interface Ethernet 0/0 ip address 192.168.1.1 255.255.255.0 no ip route-cache no ip mroute-cache interface Ethernet 0/1 shutdown
Example 1: show archive config differencesip subnet-zero ip routing router ospf 1 network 192.168.1.0 0.0.0.255 area 0 interface Ethernet 0/0 shutdown interface Ethernet 0/1 ip address 192.168.1.1 255.255.255.0 no ip route-cache no ip mroute-cache
show archive config differences scp://scpuser@server/iosconfig1.cfg scp://scpuser@server/iosconfig2.cfgThere is also a second version of the diff utility for IOS that compares a configuration file with the running configuration and tells you what lines are in the config file that are not in the running configuration. This command is show archive config incremental-diffs <filename>. It is useful to compare a previous archive to the running configuration to see what had been deleted from a configuration.
+ip subnet-zero interface Ethernet 0/0 +shutdown +interface Ethernet 0/1 +ip address 192.168.1.1 255.255.255.0 +no ip route-cache +no ip mroute-cache interface Ethernet 0/0 -ip address 192.168.1.1 255.255.255.0 -no ip route-cache -no ip mroute-cache interface Ethernet 0/1 -shutdown
My next post will look at the tools that IOS provides to do configuration replacement and rollback using archived configurations.