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Recently I'm experiencing networking issues in my LAN. I have an Ubuntu server doing PDC, mailserver and Asterisk. There's KVM on it, which runs a Windows VM and pfSense firewall. From time to time the SIP phones continuously deregister, resulting in call drops.

Last time this happened I debugged a SIP IP and the diagnosis was a generic network problem which caused the client to try registration several times before it succeded. The first connection was made with a very high CSeq (IIRC). I changed all network cables of the SIP phones (mostly Siemens Gigaset) and the disconnects went away. For some weeks, because since few days they're still coming and going, but nothing was changed on the physical LAN. The only change I made was to switch pfSense NICs to e1000 instead of virtio, this because of other reasons.

So given that it's not:

  • network cables, as they're new
  • switch: there are two switches in the LAN. I tried moving all the phones and the server on the same switch, but it still disconnect
  • pfSense: phones goes directly on the server (on the bridge interface)

How can I investigate what's wrong with the network, causing phones to disconnect? How can I understand what's wrong on the LAN?

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What are the asterisk logs showing you around the time of the disconnect event? Is it all clients at once that lose their registration, or is it unpredictable?

When calls drop do the clients hangup on their own (receive a SIP-goodbye) or are the users getting dead-air hangup then see the client is offline (due to the de-registration failing earlier in the call). If the SIP registration is failing but the RTP conversation is still up it could be one thing, if both RTP and SIP communication end at the same time it could be another issue. How frequently is your server polling the endpoints?

Is it happening with calls after a given time? This could indicate a network timer closing the session between the device and the server.

If this is predictable you could start capturing conversations between a end point and the server, and in time you may identify a network device that is giving you the problem.

  • Sadly it's unpredictable. I found no event which triggers the error, also because it happens for different IP in different times (not all together). It doesn't happen after a certain time, and may happen even if the client is NOT in a conversation. – Maxxer Mar 30 '17 at 10:42

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