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?