said by DogFace05 :

That's an all too common misconception. The reality is that Linksys/Sipura ATAs will happily run with both lines sharing the same port number. Try it and you'll see. I used to make the same assumption until low and behold, one day by accident I ended up with both lines of my adapter set to the same port, and to my surprise it was accepted just fine. As it turns out, the lines are identified and differentiated by their associated user id, so they do not each need to have their own distinct port number.

said by DogFace05 :

That's an all too common misconception. The reality is that Linksys/Sipura ATAs will happily run with both lines sharing the same port number. Try it and you'll see. I used to make the same assumption until low and behold, one day by accident I ended up with both lines of my adapter set to the same port, and to my surprise it was accepted just fine. As it turns out, the lines are identified and differentiated by their associated user id, so they do not each need to have their own distinct port number.

said by joako :

Not sure about the Cisco but for the Linksys set the following, no need to forward ports. Everything else leave default except for whatever settings are needed for your ITSP.

NAT Mapping Enable: YESNAT Keep Alive Enable:YESNAT Keep Alive Msg: $NOTIFY NAT Keep Alive Dest: $PROXY Handle VIA received: YESHandle VIA rport: YESInsert VIA received: YESInsert VIA rport: YESSubstitute VIA Addr: NOSend Resp To Src Port: NOSTUN Enable: NOSTUN Test Enable: NO

said by artisticcheese :

Gizmo Project and VOicestick.
One ATA is SPA 2002 and another one CISCO IP Phone 7960

said by jensjewels :

This is a great thread. I for one am learning lots from it :D

said by joako :

Not sure about the Cisco but for the Linksys set the following, no need to forward ports. Everything else leave default except for whatever settings are needed for your ITSP.

NAT Mapping Enable: YESNAT Keep Alive Enable:YESNAT Keep Alive Msg: $NOTIFY NAT Keep Alive Dest: $PROXY Handle VIA received: YESHandle VIA rport: YESInsert VIA received: YESInsert VIA rport: YESSubstitute VIA Addr: NOSend Resp To Src Port: NOSTUN Enable: NOSTUN Test Enable: NO

said by christcorp :

P.S. If you have a 2 LINE VOIP ADAPTER; like a PAP2; then the 1 IP address is running to voip circuits. In that case, you have to make sure the 2 different voip channels are on different ports. But individual adapters don't matter.

said by jensjewels :

Use the SIP Port field.

said by artisticcheese :

So how does this work. I have 2 VOIP providers which expect me to register with their servers at UDP 5060. I have 1 public dynamic IP on router which I can do port forwarding with. What exactly I'm supposed to enter on ATAs for those 2 different VOIP providers for them to use a different port?

said by DracoFelis :

However, you always have the option to bypass these limits/issues by putting each VoIP adapter on different ports, and then telling your router to forward specific ports to specific VoIP adapter. Because in that case, which ports you use will uniquely identify the adapter to send the traffic to.

said by joako :

Simple answer if you have a decent NAT router it will just work.

said by priller :

Your VoIP provider's SIP proxy knows the address and port you registered from, so it just sends the INVITE to you on that port.

In my example above, the INVITE comes to me on 1061 ... is translated back to 5060 and is passed along to the ATA.

--

Please don't screw with port forwarding. If for some reason you have a problem receiving calls, the problem is that the NAT translation in your router is timing out. This is resolved by adjusting the timeout in your router. If that isn't an option, then request that your provider increase the registration interval or enable NAT keepalive on the ATA.

said by artisticcheese :

How this will work for incoming call?

said by garys_2k :

Another thing to keep in mind is that all SIP traffic, and the RTP traffic that the SIP traffic sets up, originates FROM the ATA which is behind the router. Port forwarding should not be needed for any ATA. It's the router's job to keep track of which internal IP sent a request out to which external IP and route the reply back -- it is the essence of NAT.

You can have multiple PCs browsing the same web page and the router will keep track of which machine just asked for the page to be refreshed, it's no different. ATA traffic is UDP but those incoming packets are not unsolicited.

said by Cal96 :

(remembering to forward those ports in your router config).

said by artisticcheese :

I thought UDP are packets are sent and received on the same port number so on router side it shall be receiving also on 5060?

said by artisticcheese :

How on IP level it'll work if you have several ATA on internal network with different VOIP providers using the same SIP port number.