Configure a SIP trunk

1. In the Voice Routing group, click the Trunk Configuration tab.

2. Click New. Then click Pool trunk.

3. In the Select a Service dialog box, select the IP/PSTN gateway, which is your CIC server or DNS AAAA or A record name that you configured earlier.

4. Click OK.

   The name of the service appears in the Name box in the New Trunk Configuration dialog box.

5. In the Maximum early dialogs supported box, use the default value of 20.

   This value specifies the maximum number of forked responses the PSTN gateway can receive to an invite that it sent to the Lync mediation server.

6. Under Encryption support level, select Required.

7. If the following boxes are not selected, select them:

   Check box	Description
   Enable media bypass	Media bypasses the Lync mediation server and is processed by the trunk peer.
   Central media processing	Indicates that there is a well-known media termination point, such as a PSTN gateway where the media termination has the same IP address as the signaling termination.
   Enable refer support	Indicates that the trunk peer supports receiving SIP REFER requests from the Lync mediation server. (In Lync Server 2013 this parameter is already set to true in the default configuration.)

   For more information about these options, see the Lync Server Control Panel help.

8. Click OK to save the configuration.