Administrators are frequently required to limit media ports that are used by Communications Server 2007 R2 clients. This particular task is straightforward to perform for Office Communicator 2007 R2 clients through group policy. For details, see Media Port Range Registry Keys.

However, Office Communicator 2007 R2 Phone Edition is not configurable through group policy and to achieve the same result with Communicator Phone Edition, you have to edit relevant server-side pool settings so devices can receive this information through in-band provisioning in the SIP channel.

I have published an article on NextHop describing the exact procedure to limit media ports for Communicator Phone Edition devices. Complete article can be found at Limit Media Ports in Office Communications Server 2007 R2 Devices