View on
MetaCPAN is shutting down
For details read Perl NOC. After June 25th this page will redirect to
Oliver Gorwits > App-iosdiff-1.112160 > iosdiff


Annotate this POD


View/Report Bugs
Source   Latest Release: App-iosdiff-1.200001


iosdiff - Cisco IOS Config Diff Utility


version 1.112160


 $> iosdiff

 ~~~ Config diff for device
 - snmp-server enable traps ccme
 + snmp-server enable traps srst


The iosdiff program will intelligently diff two files which are in Cisco IOS-style configuration file format.

Whilst an ordinary diff works on IOS-style configuration files, it doesn't show the context in a useful way. For example if one line changes within an interface configuration, you're likely not to see the interface name in a standard 3-line contextual diff. This program improves that by showing the full context of any difference.

In terms of IOS-style configuration, this context means either the "section" such as an interface or class-map (a header with indented lines), or the command group such as an access control list, where the lines share common leading text.


The iosdiff command takes only two arguments, which are the names of the two files to diff.

 $> iosdiff from-this-file to-this-file

Lines in the files which are comments (begin with "!") will be stripped from the file before the comparison is made.



Use this option to suppress the banner which is printed before the diff output. Of course, no banner is printed anyway if there's no difference between the two files being compared. The banner looks like:

 ~~~ Config diff for device

The device name in the banner depends on the name of the "right hand" file provided for comparison (that is, the second file name passed in the command line arguments). If there's an IP in the file name, it is resolved to a host name using the DNS and printed. Otherwise the IP is used, but if there's no IP then the file name itself is used.

 $> iosdiff -B from-this-file to-this-file


You can provide a file with a list of devices to ignore. If the device having its configuration diffed is mentioned in the file, the program exits silently.

The name of the device is the "right hand" file provided for comparison (that is, the second file name passed in the command line arguments). For RANCID, not that this will probably have a suffix of ".new".

The file used for this list is /etc/iosdiff-ignore. Patches are welcome to make this feature smarter. Its contents should be one name per line, only.


If you use RANCID with Subversion, edit the RANCID user's ~/.subversion/config to contain the following line:


The effect will be that this program is called instead of the system diff utility, and smarter output produced in email notices.



Unfortunately where the difference between files is within the comments lines, RANCID will emit a notice about the difference, but you'll get nothing more. That's because comments are ignored by this program. The fix would be to patch RANCID to spot when the diff program emits no output.

Also, if you use RANCID for devices which do not save IOS-style configuration files, then setting diff-cmd=iosdiff will probably not be as useful. There is no workaround, as it's a global setting for RANCID.

Use with patch Utility

The contextual diff output produced by this program is not suitable as input to the patch utility.


Oliver Gorwits <>


This software is copyright (c) 2011 by University of Oxford.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

syntax highlighting: