What the EXTERNAL client protocol setting means

The client protocol field on a VICIdial phone record controls how the system expects to reach the audio device when an Agent logs in. Setting it to EXTERNAL tells VICIdial that no SIP registration will arrive from this Extension. Instead of waiting for a device to register, the dialer reads the dialplan number on the phone record and places an outbound call to it the moment the agent submits their login credentials.

Registration vs dial-out: what each protocol path does

With a standard SIP client protocol, VICIdial expects the device to register against Asterisk using the extension and a registration password. When an agent logs in, the system looks for an active SIP (Session Initiation Protocol) registration tied to that extension and bridges audio to it. If no registration exists at login time, the session may appear to succeed in the browser while the agent hears nothing, because the audio path is missing.

With EXTERNAL, that registration lookup is skipped entirely. VICIdial does not check Asterisk for a registered SIP peer because it does not expect one. It reads the Dialplan number field from the phone record and instructs Asterisk to dial that number via the trunk. The call goes out through whichever route your dialplan assigns to that number, the agent answers their real phone, and the two call legs are bridged into the session.

Protocol decision flow

flowchart TD
  A["Agent submits login"] --> B{"Client protocol on phone record?"}
  B -->|"SIP"| C["Check Asterisk for active SIP registration"]
  C --> D{"Registration found?"}
  D -->|Yes| E["Bridge audio to registered SIP device"]
  D -->|No| F["No audio path — agent hears silence"]
  B -->|"EXTERNAL"| G["Skip registration check"]
  G --> H["Read dialplan number from phone record"]
  H --> I["Asterisk dials number via trunk"]
  I --> J["Agent answers real phone"]
  J --> K["Audio bridged — session active"]

Pairing client protocol with phone type

The client protocol EXTERNAL setting works in tandem with phone type external. Both fields need to be set correctly on the same phone record. Setting only one leads to inconsistent behavior: phone type external tells the record-creation logic what kind of device this represents, while client protocol EXTERNAL tells the runtime engine which connection method to use when the agent logs in. A phone record intended for a home or mobile agent needs both values set.

Other client protocol options and when EXTERNAL applies

VICIdial supports other client protocol values for different device types. SIP values apply to standard SIP Hardphone (deskphone) or Softphone devices that register on the server. There is also a Webphone protocol for WebRTC-based browser clients. Choose EXTERNAL when the agent's audio comes from any phone number reachable by your carrier — a home landline, a mobile, a forwarding service — and when that device cannot or should not run a SIP client.

Any scenario where the dialer must initiate the audio path, rather than receiving an inbound registration from the agent's device, maps to the EXTERNAL client protocol. Monitoring entries for supervisors on mobile are another common use: the supervisor's mobile number is dialed at login and they can listen to calls without any VoIP app installed.

For a full step-by-step walkthrough of the phone record, see how to run a VICIdial agent on a home phone. The remote agents guide puts client protocol in context alongside the other external phone fields. If you want a managed VICIdial server ready in under 40 seconds without building the stack yourself, see our pricing page.