Trunk

A trunk is a communication channel that connects VICIdial’s Asterisk PBX to an external carrier or telephony provider. In modern VICIdial deployments, trunks are almost always SIP-based connections that carry multiple concurrent calls over a single IP connection, replacing the physical T1/PRI lines used in legacy telephony.

How It Works in VICIdial

SIP trunks in VICIdial are configured as SIP or PJSIP peer entries that define the connection parameters to a carrier. Each trunk configuration includes the carrier’s IP address or hostname, authentication credentials, supported codecs, DTMF mode, and concurrent call limits. VICIdial’s dialplan routes outbound calls through specific trunks using dial prefixes.

A single SIP trunk can typically handle hundreds of concurrent calls, limited only by bandwidth, server capacity, and the carrier’s provisioned channel count. VICIdial supports multiple trunks simultaneously, enabling failover routing — if one carrier is unreachable, calls route through an alternate trunk.

Inbound trunks receive calls on DIDs provisioned by the carrier. The trunk delivers the call to Asterisk, which matches the dialed number to VICIdial’s DID routing table and sends the call to the appropriate inbound group or call menu.

Why It Matters

Trunk capacity directly determines how many simultaneous outbound and inbound calls your VICIdial system can handle. Under-provisioned trunks create bottlenecks — the hopper has leads ready and agents are waiting, but calls cannot be placed because all trunk channels are in use. Over-provisioned trunks waste money on unused capacity.

A general rule is to provision 1.5x the expected concurrent call count to accommodate predictive dialing overhead. Multi-carrier trunk configurations provide both failover redundancy and cost optimization by routing calls through the least expensive available path. See the VICIdial setup guide for trunk sizing guidelines.