Use the Application Routing module to force all SIP tcp/udp 5060 traffic out the preferred WAN interface. Also create a rule to force all UDP 10000-20000 traffic out the same interface.
Application Routing can be found in the AppRouting Tab for 4.X firmware
Article ID: 36, Created: February 23, 2015 at 3:01 PM, Modified: February 24, 2015 at 8:42 PM