Preferred SIP Port

When a SIP interface contains multiple SIP ports of the same transport protocol, a preferred SIP port for each transport protocol is selected for outgoing requests when the specific SIP port cannot be determined. When forwarding a request that matched a cached registration entry (HNT or normal registration caching), the SIP port upon which the original REGISTER message arrived is used. Otherwise, the preferred SIP port for the selected transport protocol is used. When selecting the preferred SIP port, the default SIP port of 5060 will be selected over other non-default ports.

For SIP interfaces using the SIP NAT function, the preferred SIP port address and port will take precedence over the external address of the SIP NAT when they do not match. If both TCP and UDP SIP ports are defined, the address and port of the preferred UDP port is used.