I’ve been using Nagios for ages to monitor the Crossed Wires campus network, but it’s fallen into a little disrepair.  Nothing worse than your monitoring needing monitoring…  so I set about tidying it up. Network topology changes, removal of old kit, and some fixes to service checks no longer working correctly.

One of the problems I needed to fix was the service check for IAX connections into my Asterisk box.  The script (the standard check_asterisk.pl from the Nagios Plugins package) was set up correctly, but it would fail with a “Got no reply” message.

I started doing traces and “iax2 debug” in Asterisk, but got nowhere — Asterisk was rejecting the packet from the check script.  Finally I decided to JFGI, and eventually I found this page with the explanation and the fix.  Basically, sometime in the 1.6 stream Asterisk toughened up security on the control message the Nagios service check used to use.  Thankfully, at the same time a new control message specifically designed for availability checking was implemented, and the fix is to update the script to use the new control message.  Easy!

BTW, while on Nagios, I got burned by the so-called “vconfig patch” which broke the check_ping script.  I’ve had to mask version 1.4.14-r2 and above of the nagios-plugins package until the issue is fixed.

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