Carrier won't register: what to check

When a Carrier will not register, the cause is almost always one of five things: a typo in the Registration string, the wrong host or port, NAT in the path, bad credentials, or a firewall blocking port 5060. Work the checklist in order and you will usually find it in minutes.

Confirm what Asterisk thinks is happening

Start on the Asterisk CLI. Run sip show registry to see the registration attempt and its state, and sip show peers to see whether the SIP peer is reachable. A registry line stuck in a non-Registered state tells you the SIP registrar on the carrier side is rejecting or never seeing your request. That status points you at which part of the checklist to dig into.

flowchart TD
  A[Register fails] --> B[Check registration string for typos]
  B --> C[Verify host and port]
  C --> D[Confirm credentials]
  D --> E[Check NAT settings]
  E --> F[Open firewall on 5060]
  F --> G[sip show registry = Registered]

Walk the checklist

Go through these one at a time. Most failed registrations are a single small mistake.

1. Registration string typos: the register line must read exactly user:pass@host with the right port. A stray space, a wrong colon, or an extra character breaks the whole line.
2. Host and port: confirm the carrier hostname resolves and that you are using the port they specified, usually 5060 for SIP but not always.
3. Credentials: re-check the username and secret against what the carrier issued. Many carriers use a separate auth username from the account label.
4. NAT: if anything sits between your server and the carrier, registration can succeed but media fails, or the register never completes. On a public-IP box this is rarely the issue.
5. Firewall on 5060: make sure UDP 5060 (and the RTP range) is open to the carrier in both directions, and that the carrier has not blocked your IP.

The order matters. A typo in the register line and bad credentials both produce a failed registration that looks identical from the dialer, so checking the string character by character before you start poking at the firewall saves time. Copy the register line the carrier gave you verbatim rather than retyping it, since hand-entered strings are where most typos creep in. If the carrier sent you a username that differs from your account name, that mismatch alone will block every register attempt.

Confirm it stuck

After each change, save the carrier, wait about a minute for the conf files to regenerate, then run sip show registry again. When the registration shows Registered and the peer is reachable, place a single test call to confirm the trunk actually carries audio. This troubleshooting flow is part of the wider VICIdial carrier integration guide, and if you are still deciding whether to register at all, registration versus IP authentication covers the trade-off.

On a VICIfast box you get a fixed public IP and no NAT in the way, which removes two of the five usual registration headaches before you even start. The dialer provisions over HTTPS in under 40 seconds.