Aastra 9143i Series Administrator's Manual page 219

SIP and TLS Source Ports for NAT Traversal
A System Administrator can configure the SIP and TLS source ports on the IP
Phone. Previously, the IP phone used default values (5060 for UDP/TCP and 5061
for TLS). The two new parameters for configuring the SIP and TLS source ports
are:
• sip local port
• sip local tls port
You can configure the SIP and TLS source ports using the configuration files or
the Aastra Web UI. After configuring these parameters, you must reboot the
phone.
If NAT is disabled, the port number also shows in the VIA and Contact SIP
headers.
If you enable NAT, the phone uses the NAT port number (and NAT IP address) in
the Via and Contact SIP headers of SIP messages, but still use the configured
source port.
41-001160-03, Rev 00, Releaes 2.4
Configuring Network and Session Initiation Protocol (SIP) Features
Note: 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.If
symmetric UDP signaling is disabled, the phone sends from random
ports but it listens on the configured SIP local port.
Network Settings
4-37