A single trunk is created when a new PSTN gateway is being defined, but administrators can always create additional trunks to the same PSTN gateway later with the new M:N trunk routing support. To create a new trunk to an existing PSTN gateway, follow these steps within Topology Builder:
1. Expand Shared Components, right-click on Trunks, and select New Trunk.
2. Enter a Trunk Name, which represents the connection between a Mediation pool and a gateway with a unique port combination.
3. Select an Associated PSTN Gateway.
4. Enter a Listening Port on the IP/PSTN Gateway where calls will be sent.
5. Select whether to use TCP or TLS as the SIP Transport Protocol.
6. Select an Associated Mediation Server pool ...