Polycom realpresence 1800 Administrator's Manual page 537

Settings in the Ports tab allow specific ports in the firewall to be allocated to multimedia conference
calls.
The port range recommended by IANA (Internet Assigned Numbers Authority) is 49152 to 65535.
The Collaboration Server uses this recommendation along with the number of licensed ports to
calculate the port range.
11 Modify the following fields:
Default IP Service – Conferencing – Ports Parameters
Field
Fixed Ports
Polycom, Inc.
Description
Leave this check box cleared if you are defining a Network Service for local calls
that do not require configuring the firewall to accept calls from external entities.
When cleared, the system uses the default port range and allocates 4 RTP and
4 RTCP ports for media channels (Audio, Video, Content and FECC).
Note: When ICE Environment is enabled, 8 additional ports are allocated to
each call.
Click this check box to manually define the port ranges or to limit the number of
ports to be left open.
IP Network Services
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