Restrict Extension Registration Based on User Agent

This topic describes how to restrict extension registration based on user agent.

Background information

SIP is a peer-to-peer protocol. The peers in a session are called User Agents (UAs). A user agent can play one of the following roles:
  • User Agent Client (UAC): A client application that initiates a SIP request, such as INVITE, ACK, OPTIONS, BYE, CANCEL, and REGISTER.
  • User Agent Server (UAS): A server application that receives the SIP request from a UAC, and returns a response to the request back to the UAC.

When a SIP endpoint tries to register an extension to Yeastar P-Series Software Edition, the SIP endpoint working as UAC sends packets containing user agent string to the PBX. By default, Yeastar P-Series Software Edition allows registrations from any UAC without authenticating user agent. For security reasons, you can restrict extension registration based on user agent.


  1. Log in to PBX web portal, go to Extension and Trunk > Extension, edit the desired extension.
  2. Click Security tab.
  3. In the SIP Security section, select the checkbox of Enable User Agent Registration Authorization.
  4. Set the user agent.
    1. Click Add User Agent.
    2. In the User Agent field, enter a value.
  5. Click Save and Apply.


When a phone is trying to register an extension, the phone will send SIP packets containing a user agent, such as phone manufacturer, phone model, etc. If the prefix of the user agent does not match the specified value, the registration will fail.