You’d not believe the number of others routers we have had issues with that do not support “SIP ALG (Application Layer Gateway)” properly, Peplink’s routers are one of ones we’ve been using seamlessly with VoIP services that have a remote or virtual SIP Server.
[quote=""]Application-level gateway - Wikipedia
For instance, for Session Initiation Protocol (SIP) Back-to-Back User agent (B2BUA), an ALG can allow firewall traversal with SIP. If the firewall has its SIP traffic terminated on an ALG then the responsibility for permitting SIP sessions passes to the ALG instead of the firewall. An ALG can solve another major SIP headache: NAT traversal. Basically a NAT with a built-in ALG can rewrite information within the SIP messages and can hold address bindings until the session terminates.
Happy to Help,