RADIUS sniffer

Nicolas Baradakis nbk at sitadelle.com
Thu Jan 19 17:09:17 CET 2006

When debugging a problem in prod environment, it's not possible to
restart FreeRADIUS in debug mode, so we have to use a sniffer to
display the RADIUS traffic on the network. However, general purpose
sniffers like tcpdump or ethereal can only decode a few RADIUS
attribute, while FreeRADIUS has thousands of attributes in its

That's why I wrote a simple sniffer based on the libradius of
FreeRADIUS. It prints the RADIUS packets exactly like running
"radiusd -X". It can also filter the packets based on any RADIUS
attributes: the sniffer accepts the same strings as the "users" file
to match a packet. I think it's a very useful RADIUS debug tool.

As it's easier to build the sniffer in the FreeRADIUS source tree,
I've made a patch against CVS head. It is available here:


If people would be interested, it can be added to the CVS tree (pending
Alan's approval).

Nicolas Baradakis

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