VICIdial Registration String: Registering With Your Carrier

The Registration String is the field that decides whether your carrier knows where to send your calls. Get it right and inbound calls find your server. Get it wrong, or leave it blank when you needed it, and your numbers ring into the void. It is one line of text, but it carries weight.

This post explains what the Registration string does, the exact format, when you actually need one, and how to confirm registration worked. It is one field on the carrier form covered in adding a carrier trunk.

What registering means

Registering is your server telling the carrier "I am here, this is who I am, send my calls to this address." The carrier acts as a SIP registrar — a server that records the current location of your trunk. When someone dials one of your numbers, the carrier looks up that registration and delivers the call to wherever you last announced yourself. Without a current registration, the carrier has nowhere to send inbound calls.

This matters most for inbound. Outbound calls usually go out fine without registration because your server initiates them. But if you want a DID (direct inward dialing) to reach your agents, the carrier has to know your location, and registration is how dynamic-host setups provide it.

The format

VICIdial passes the Registration String straight into the SIP, PJSIP, or IAX config, so it must match what your provider expects. The classic SIP (Session Initiation Protocol) form is:

register => username:secret@carrierhost:5060

Read it left to right: the word register, then your login and password, then the carrier's host and port. Your provider's setup sheet gives you these values verbatim. Do not invent them — even a wrong port silently breaks registration.

When you do not need it

Not every Carrier uses registration. Many providers prefer IP authentication instead: you give them your server's static IP, they whitelist it, and they route calls to that IP directly. No username, no secret, no register line. In that model the Registration String stays blank and the carrier identifies you purely by where the traffic comes from.

Registration and IP auth are two answers to the same question — how does the carrier find you. The flow below shows which path applies. We compare the two head to head in register vs IP auth.

flowchart TD
  A[Carrier setup sheet] --> B{Auth method?}
  B -->|Dynamic host| C[Fill Registration String]
  B -->|Static IP| D[Leave string blank]
  C --> E[Server registers to carrier]
  D --> F[Carrier whitelists your IP]
  E --> G[Inbound calls routed]
  F --> G

Confirm it worked

After you save the carrier and set Active=Y, wait about a minute, then check from the Asterisk CLI. Run "sip show registry" to see your outbound registrations and their status, or "sip show peers" to see whether the carrier peer is reachable. A healthy registration shows your trunk as registered with a recent timestamp. If it shows Auth or Failed, recheck the username, secret, and host one character at a time.

When registration just will not take, work through the not-registering troubleshooter. The whole carrier picture lives in the carrier integration guide.

Wrap up

The Registration String is a single line, but it is the difference between a DID (direct inward dialing) that rings your agents and one that goes nowhere. Match the format your carrier gives you, set the trunk Active, and confirm in the CLI. Need a server to register from? VICIfast provisions one in under 40 seconds — see pricing.