A trunk is a communications line or link designed to carry multiple signals simultaneously to provide network access between two points. Trunks typically connect switching centers in a communications system.
Trunks have two options:
An IP address can be assigned to a Trunk (Group) alongside a port. The default is 5060, and port 1 signifies the switch to allow any port from the specified IP address.
A SIP Registration can be configured to the switch's IP(s)