Aastra Telecom 9480i CT Series User Manual

41-001160-03, Rev 00, Releaes 2.4 

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Configuring Advanced Operational Features

By default, the IP phones use symmetric UDP signaling for outgoing UDP SIP 
messages. When symmetric UDP is enabled, the IP phone generates and listens 
for UDP messages using port 5060. 

You can manually disable symmetric UDP signaling using the IP phone’s 
configuration file. When you disable symmetric UDP signaling, then the IP phone 
chooses a random source port for UDP messages. 

The IP phone also chooses a random source port for UDP messages if you 
configure a backup proxy server, registrar server, or outbound proxy server.

An Administrator can configure symmetric UDP signaling using the configuration 
files only.

You use the following parameter to enable or disable Symmetric UDP Signaling 
in the configuration files:

For the specific parameter you can set in the configuration files, see Appendix A, the section, 

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