We have two offices each with a Sonicwall Pro 2040 connected via site to site VPN. Each site has a Panasonic pbx with a voip port into their local LAN.
No VLAN or QoS have been enabled yet, but the setup had been working (though not particularly well) for several years. Suddenly just this week, however, when dialing an extension from one site to another - all audio will just cut out after exactly 12 seconds, every time. No changes had been made recently to either of the Sonicwalls or the Panasonics. Data traffic between the LANs across the VPN seems unchanged.
We downloaded the Panasonic voip test tool and installed on PCs at both sites. When run between PCs across the VPN all test fail - (TCP, UDP, SIP, H.323). When run between PCs within the same LAN all tests pass. The default firewall rules allowing all services to pass from remote LAN to local LAN (and reflexively) is present on both Sonicwalls
I've just put in the allow any VOIP traffic firewall rule described in the solution to this similar question and am waiting for feedback from users in the morning.
Any help on this greatly appreciated!