Set Up a Backup Carrier for VICIdial Failover

Add a second carrier and failover routing so calls reroute automatically when your primary trunk returns a 503 or congestion instead of completing.

A backup carrier is a second Carrier plus routing that automatically retries on the backup when your primary Trunk cannot complete a call. When the primary returns a SIP 503 Service Unavailable or CONGESTION, the dialplan falls through to the backup instead of just dropping the lead.

Add the second carrier

Add the backup as its own carrier entry under Admin then Carriers, with its own account block, Registration string or IP authorization, and a distinct Carrier ID. Stage it, confirm its SIP peer is reachable with sip show peers, and place one test call so you know it works on its own before you ever rely on it as a fallback. A backup you have never dialed through is not a backup.

Pick a backup carrier on a different network or provider than your primary. Two trunks that share an upstream can fail at the same moment, which defeats the purpose.

Add failover routing

The mechanism is Failover inside the outbound dialplan. You dial the primary trunk first; if that attempt comes back with a busy or unavailable response, the next dialplan priority tries the backup trunk for the same number. VICIdial reads the dial status and falls through rather than hanging up.

flowchart TD
  A[Outbound call placed] --> B[Dial primary carrier]
  B --> C{Primary completes?}
  C -->|Yes| D[Call connects]
  C -->|503 or congestion| E[Dial backup carrier]
  E --> F{Backup completes?}
  F -->|Yes| D
  F -->|No| G[Report failure to dialer]

The responses worth failing over on are the ones that mean the carrier itself is the problem, not the destination number.

A 503 service-unavailable usually means the carrier is overloaded or refusing traffic right now.
Congestion or a chanunavailable result points at a trunk or capacity problem on the carrier side.
A plain busy or a number-specific reject is about the called party, so failing over there just doubles the work.

Be selective about which responses trigger failover. If you retry every failed call on the backup, you can flood the second carrier and push your concurrent-channel usage past what either provider allows.

Set the backup up the same way you set up the primary. Give it its own account block with disallow=all then allow=ulaw to pin the codec, set host to the carrier IP or dynamic depending on whether they use IP authorization, and give it a clean dial pattern. The strip and prefix on the backup do not have to match the primary, but the number format you hand the backup carrier still has to be one it will route.

Test the fallback path

Prove the failover actually fires. The simplest test is to temporarily deactivate the primary carrier and confirm calls still complete through the backup, then reactivate the primary. Once you have seen a call route over and connect, you know the path is real and not just configured. A backup that is configured but never exercised has a way of failing exactly when you finally need it.

It is also worth re-testing the fallback after any change to the primary carrier. If you edit the primary dialplan or change its strip, make sure you did not accidentally break the priority that hands off to the backup. Place one manual call from Campaign Detail after the edit and watch which trunk carries it.

Backup carriers sit alongside the rest of the carrier work in the VICIdial carrier integration guide, and the full multi-carrier picture is in running multiple carriers with failover.

Because a VICIfast box is single tenant with a fixed public IP, both your primary and backup carriers authorize the same server, and your dialer is live over HTTPS in under 40 seconds. Adding a second trunk is one more carrier entry, not a second machine.