Given that Phone Proxies are analogous to Termination Customer Trunks, Termination Vendor Trunk Groups are used to forward the SIP Registrations to the customer’s PBX. These Trunk Groups should be created in the customer’s Relationship.
The Termination Vendor Trunk Groups are assigned to associated with the Phone Proxy Mode connection Transport Proxy by selecting the Trunk Group in the Main Registrar down-down list in the Phone Proxy Mode connection.
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Create a Trunk Group for each protocol that the SIP Phones are configured to use.