We have a problem where some of our Polycom phones which connect through our TZ105 Sonicwall to a hosted PBX will go unreachable.
under VOIP Settings of the TZ105 we have:
Enable consistent NAT
Enable SIP Transformations
However when we look in the log of the FW it says "UDP Packet Dropped" destined for the very device which goes unreachable. It only does this for one or two of our 17 phones and it seems to change which phone it is periodically.
We set an allow rule for the IP of the hosted PBX and this did not change the dropped packets. For some reason it is dropping the keep alive packets for just a few phones. I have not seen a pattern as to which phone it is.
The hosted PBX Is running FreePBX. I have tried changing the NAT settings on the PBX between Yes, no, never and route without much noticeable difference in behavior.
For some reason one or two phones will not stay registered and therefore not receive calls. They are able to make calls.
This is my first Sonicwall