Using non-default local ports in your phone settings can avoid many of the most commonly encountered router and firewall related problems.
For two or more SIP terminals (VoIP phones) to function reliably behind the same router, each SIP Terminal should use different local UDP ports.
Even if you are using a single device only, changing the default 'Local' or 'Listen' ports used by your VoIP phone can avoid many potential router related issues.
Most VoIP phones and devices will be pre-configured to use the following ports:
- Listen SIP Port: 5060
- Listen RTP Port: 5004
Instead, set your first VoIP phone to use:
- Listen SIP Port: 46160
- Listen RTP Port: 46104
For the next VoIP phone use:
- Listen SIP Port: 46260
- Listen RTP Port: 46204
For additional VoIP phones or devices, continue increasing the ports so that each additional phone uses a successive SIP port like:
46160, 46260, 46360, 46460, etc
and the same for the starting RTP port:
46104, 46204, 46304, 46404, etc.