Trunk

A trunk is the pipe between your VICIdial server and the outside phone network. When VICIdial dials a number, the call leaves your server through a trunk and onto your carrier, who passes it to the regular phone system. Calls coming back in arrive the same way. Think of it as the road every call has to travel — your dialer can be perfectly configured, but if the road isn't open, nothing moves.

Without at least one working trunk, the dialer can't place a single call — it's the most basic thing you have to set up. Most modern trunks run over sip (Session Initiation Protocol), though some older setups still use iax2 (Inter-Asterisk eXchange version 2). Either way, the trunk is where you enter the username, password, and server address your carrier gave you. Get one digit wrong and the calls simply won't go through.

Outbound and inbound

Trunks work in both directions. On the way out, VICIdial may add a phone number prefix to route the call down a specific trunk — handy when you have one carrier for cheap minutes and another for better delivery. On the way in, your trunk is what a did (Direct Inward Dialing number) rides on so callers reach your campaigns. Many shops run several trunks at once and split traffic between them, sending different area codes or different campaigns down whichever route performs best.

If you see lots of fast busy signals or congestion errors, the trunk is a good first place to look. It can mean the carrier is rejecting calls, your channel limit is maxed out, or the login details are wrong. A clean trunk should connect quietly and stay registered around the clock.

It matters because the trunk is where carrier problems and dialer problems meet. When calls are failing, knowing whether the trunk is healthy tells you which side of the fence to look on — your settings, or your carrier's network. That one distinction saves a lot of wasted troubleshooting.