What is the VICIdial phone extension?

The Phone extension field is the name of your phone as Asterisk sees it, with one twist: you leave off the protocol and the slash at the front. It is the part after the slash, not the whole thing. Getting this field right is the difference between a phone that registers and one that Asterisk never recognizes, so it is worth a minute to understand exactly what goes in it.

It is the name without the protocol prefix

Inside Asterisk, a device is named with its protocol, a slash, and then its identifier, like SIP/test101. In the VICIdial Phone extension field you put only the part after the slash. So for the SIP (Session Initiation Protocol) phone SIP/test101 the Phone extension is test101. The SIP and the slash do not go in the field; they are described by the separate Protocol field instead.

The pattern holds across phone types. For an IAX2 phone written IAX2/IAXphone1@IAXphone1, the Phone extension is IAXphone1 and the Protocol is IAX2. For a channelbank phone written Zap/25-1, the Phone extension is the full channel name 25-1. The diagram shows the split.

flowchart LR
  A[SIP/test101] --> B[Protocol SIP]
  A --> C[Extension test101]
  D[IAX2/IAXphone1@IAXphone1] --> E[Protocol IAX2]
  D --> F[Extension IAXphone1]
  G[Zap/25-1] --> H[Protocol Zap]
  G --> I[Extension 25-1]

Read each row as one phone. The full Asterisk name on the left splits into the Protocol field and the Phone extension field on the right. The protocol part always moves to the Protocol dropdown, never into the extension.

The no-dashes rule for SIP, PJSIP, and IAX

For SIP, PJSIP, and IAX phones the extension must not contain any dashes. More broadly, the field accepts only letters, numbers, and dashes, with no spaces or special punctuation, and for these three protocols you drop the dashes too. So test101 is fine, test-101 is not for a SIP phone, and test 101 with a space is never valid. The Zap channelbank example is the exception where a dash is legitimate, because 25-1 is the literal channel name, but you will rarely set those up on a modern softphone-based deployment.

Match the Protocol field below it

Right under the extension is the Protocol field, and it has to match the phone type you are entering. If your device is a SIP phone, set Protocol to SIP; if it is IAX, set IAX2; if it is a channelbank, set Zap. A mismatch here means Asterisk builds the wrong kind of config for the device, and the phone will not register no matter how correct the extension looks. Treat the extension and the protocol as a pair that has to agree.

Where the extension fits

The extension is the device side of the picture; the dialplan number is what you dial to ring it, and the two are not the same field. The VICIdial phones pillar guide shows how the Extension, the protocol, the registration password, and the dialplan number all sit on one record.

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