Server Trunks: Assigning Carrier Lines at the Server Level

On a single VICIdial box, every campaign competes for the same pool of outbound lines. Without any rules, whichever campaign dials first grabs as many lines as it can, and a quiet campaign can find itself starved at peak. VICIdial Server Trunks are how you carve that pool up on purpose.

Server Trunks let you restrict the outgoing lines used on this server for campaign dialing, on a per-campaign basis. You can reserve a set number of lines for one campaign, and you can decide whether that campaign is allowed to spill over into spare lines when they are free.

The ceiling: Max VICIdial Trunks

Everything sits under one hard ceiling: the Max VICIdial Trunks setting on the server. That is the total number of Concurrent calls VICIdial will place across all campaigns on that box. Server Trunks records divide up the space under that ceiling; they never raise it. If you do not create any Server Trunks records at all, there is no per-campaign rule, and the first campaign to dial simply takes whatever it can get up to the Max.

So the mental model is two layers: the server says "no more than N lines total," and the Server Trunks records say "of those N, this campaign gets at least this many reserved."

Reserving and overflowing

A Server Trunks record does two things. First, it reserves a specific number of lines for one campaign, so those lines are held for it whether or not it is using them right now. Second, you choose whether that campaign may run over its reserved count into whatever lines remain open, as long as the total stays under Max VICIdial Trunks.

• Reserved only: a guaranteed floor, but the campaign cannot exceed it even when the box is idle.
• Reserved plus overflow: a guaranteed floor that can climb into spare capacity when other campaigns are quiet.

This pairs naturally with how a predictive Campaign paces itself. A predictive campaign will happily eat lines if you let it, so reserving a floor for your inbound or callback work keeps a hot outbound push from swallowing everything.

flowchart TD
  A[Campaign wants a line] --> B{Reserved lines free?}
  B -->|Yes| C[Use reserved line]
  B -->|No| D{Overflow allowed?}
  D -->|No| E[Wait for a reserved line]
  D -->|Yes| F{Total under Max Trunks?}
  F -->|Yes| G[Borrow a spare line]
  F -->|No| E

Where carrier capacity fits

Server Trunks govern lines on your VICIdial server. They are not the same as the channel limit your carrier enforces on its end. Your Carrier has its own cap on simultaneous calls, and if VICIdial tries to place more than the carrier allows, the extra calls fail at the trunk regardless of what your Server Trunks records say.

Set Max VICIdial Trunks at or below what your carrier will actually carry, then divide that with Server Trunks. For the full carrier-side view of how outbound calls reach the wire, see the carrier integration guide.

If you run more than one carrier for redundancy, capacity planning gets more interesting. Running multiple carriers for failover covers how to spread load when one trunk goes down.

Wrapping up

Server Trunks are a fairness tool: Max VICIdial Trunks sets the ceiling, and per-campaign records reserve floors under it with optional overflow. Use them when several campaigns share a box and one of them must never get starved.

VICIfast gives you a dedicated single-tenant box provisioned in under 40 seconds, so your line pool is yours alone and Max VICIdial Trunks is sized to the server you picked. See plans and pricing.