We have a Balance 380 (firmware 5.4.9 build 2573) with 2 WANs - 1 Fiber (20/20 Mbps) and 1 DSL (1/15 Mbps). We’ve had various intermittent issues (phones not ringing on internal and external calls, Presence feature not working, poor quality, can’t hear the other party, dropped calls) with VoIP (Ringcentral with Polycom VVX phones) for several months. We found that disabling the DSL WAN solved the all of the VoIP problems even though DSL was never used for SIP. Others have reported similar problems here which are solved by disabling one WAN.
In our environment, the Fiber WAN is more than sufficient for all sessions, but we want to configure DSL to use temporarily in the event that the fiber service fails.
On the Balance we have Outbound Policy for the VoIP network with separate rules for 2 VoIP UDP port ranges with Fiber WAN at highest priority and DSL WAN at lowest priority; we tried the Priority and Overflow algorithms with the same (bad) results regardless of algorithm.
QoS with High Priority for SIP and RTP.
Service Passthrough SIP in Compatibility mode. SIP ALG is disabled on the hidden config page.
According to Active Sessions, all SIP sessions are on the Fiber WAN; we’ve never seen a SIP session on DSL WAN.
Why does disabling the DSL WAN solve VoIP problems if DSL is never used for SIP sessions?
We will appreciate any suggestions.