Configuring multiple phones in one private network is more complicated because a port can only be used by one application at a time, and when you setup port forwarding you send all traffic received on a port to one specific device.
Before you get started, please ensure you understand the basic process for setting up one VoIP phone to work behind a router, which we outline in this help guide.
It will help if you grab some paper and write the a name for each device on your it. Then, underneath each device on your sheet of paper, write the following:
- Static IP address
- SIP communications port
- Voice data (RDP) ports
Now configure a static IP address for each device, making a note against each device which static IP has been allocated to it. In each case, ensure that you have configured this on both the router and the phone.
Now choose a SIP communications port for each phone to use. By default, this is 5060, so you can allow one phone to use this if you wish. For the others, choose a unique port, e.g. 5062 for phone two, 5064 for phone three. In each case, make a note of the port chosen for each device on your sheet of paper.
Do the same for RTP ports, which also need to be staggered in increments. Depending on how many devices you have, the port range can be staggered between 20 to 100 ports per device.
You now need to enter the chosen port onto your phone. On the phone's web interface you should find a configuration option such as Local SIP port or Local listen port. Enter the specific SIP communications port that you have chosen for the phone in here. You may need to refer to your phone's user documentation if you're not sure what to edit. We have listed some examples of what different manufacturers call this setting in the table below.
|Manufacturer||Field to edit||Where do I usually find it?|
|Grandstream||Local SIP port||On the account registration page|
|Siemens Gigaset||Local SIP port||Click on Advanced Settings|
|snom||Network identity (port)||Click on Advanced, then SIP/RTP|
|Yealink||Local SIP port||Click on Account, then Advanced Settings|
Finally choose a suitable range of voice data ports for each device to receive the audio traffic. As usual, enter these on your sheet of paper.
Now you can configure the port forwarding settings on your router. Enter port configurations for each device, as shown on your sheet of paper. Each device requires two entries (so if you had three phones in your private network you would create six entries).
It's very important that for each entry, you select the correct IP address of the phone that corresponds to it - this is where writing everything down is extremely useful. If you don't set this up correctly, you will very quickly spot strange behaviour, such as all phones ringing, no phones ringing or one way audio.