H.323 Telephone Installation
Page 28
15-601046 Issue 17e (Wednesday, November 14, 2012)
IP Office
2.2.2 Setting the RTP Port Range
The ports used for H.323 VoIP calls vary for each call. The range for the ports used can be adjusted in order to avoid
conflict with other services. If the customer has any internal firewalls or similar equipment that applies port filtering or
only forwards traffic based on the port used, the range set here must be allowed by those devices.
For each VoIP call, receive ports are selected from the range defined below. Even numbers in the range are used for the
calls incoming Real-Time Transport Protocol (RTP) traffic. The same calls Real-Time Transport Control Protocol (RTCP)
traffic uses the RTP port number plus 1, that is the odd numbers.
It is recommended that only port numbers greater than or equal to 49152 but strictly less than 65535 are used, that
being the range defined by the Internet Assigned Numbers Authority (IANA) for dynamic usage.
Checking the Port Range
1. Using IP Office Manager, retrieve the configuration from the system.
2. Select
System.
3. Select the LAN1 or LAN2 tab depending on which of the system's LAN interfaces you want to use to support
H.323 extensions.
4. Select the VoIP sub-tab.
5. Check the RTP Port Number Range shown. Remember that the matching RTCP traffic uses the same range plus
1.
·
Port Range (Minimum): Default = 49152. Range = 1024 to 65280.
This sets the lower limit for the RTP port numbers used by the system. Choosing a minimum range of less
than 1024 should only be done after careful analysis of the overall configuration.
·
Port Range (Maximum): Default = 53246. Range = 1278 to 65534.
This sets the upper limit for the RTP port numbers used by the system. The gap between the minimum and
the maximum must be at least 254. Choosing a minimum range of less than 1024 should only be done after
careful analysis of the overall configuration.
6. If these settings need to be changed, do so and then save the configuration back to the system.
