In order to allow two or more SIP terminals (VoIP phones or devices) on a network to operate reliably behind one router, please ensure each SIP terminal uses different Local Ports.
Most VoIP phones and devices will be pre-configured to use the following ports:
Instead please set your first VoIP phone to use:
For the next VoIP phone please use:
For additional VoIP phones or devices, continue increasing the ports so that each additional phone uses a successive SIP port like: 44160, 44260, 44360, 44460, etc (and the same for the starting RTP port: 44104, 44204, 44304, 44404, etc).
If your SIP device requires Start (Min) and End (Max) local RTP port values to be specified, it should be sufficient to use RTP port ranges like 44104 - 44120, 44204 - 44220, 44304 - 44320, etc.
If issues arise after changing the Local Ports used by your VoIP devices, please disable SIP ALG (click here) and Stateful Packet Inspection, SPI, options if supported by your router.
If issues still persist, please assign a static IP address to your VoIP phones and devices.
Then, in your router settings, port forward the SIP and RTP ports (UDP) used by your VoIP Phones and devices.
With port-forwarding in use, please omit any included STUN Servers from your VoIP device's settings and disable the router option UPnP.
Don't confuse sipgate's SIP server ports (which are always 5060) with your phone's Local Ports!
Some multi-line VoIP devices use a Global Local SIP port (e.g. Aastra, Siemens Gigaset and Snom devices).
Other multi-Line devices use a different Local SIP Port for each active Account or Line (e.g. Grandstream, Yealink deskphones, and Cisco/Linksys Small Business devices).
Please continue the above incremental port numbering for device that allows each active Account/Line to be given a different Local SIP Port.
The Local SIP Port is sometimes called the 'SIP Signalling Port' or 'Listen SIP Port'. The Local RTP Ports may be called the 'Audio' or 'Media' ports.
Where can I find my Phone's Local UDP Port Settings?
The following Help Article lists the location of Local Port settings in many popular phones and applications: