V-Portal behind router works without any ports forwarded

Posts: 4 · New Forum Member Joined: May 08, 2004 Posts: 4

Hi,

I see a lot of information out here, but replies are wildly different.

So, my setup is this:

Verizon FiOS MoCA -> Verison FiOS router -> Vonage V-Portal Adapter

I can't place the V-Portal in front of the router due to the fact that I have Coax incoming, not ethernet

The support pages state that I have to forward UDP 10000-20000 to the adapter.

However it just works, outgoing, incoming, everything. The adapter is not a DMZ host, nor I had any ports forwarded to it. It works fine.

Is this "normal"? As far as I understand SIP there HAS to be some incoming communication but in case of Vonage there seems to be a workaround in their own protocol implementation to work only with outgoing allowed

Am I missing something obvious?

Thanks!
Art

Posts: 656 · Posted: Wed Mar 10, 2010 6:42 pm Post subject:

People who say port forwarding is needed just do not understand the basic networking principles implemented that makes Vonage's SIP through NAT solution work. The Vonage telephone adapter will send a Registration message every 20 seconds to the Proxy server which then gets back a 200 OK. This 20 second quick registration, also known as a SIP minor Registration will keep the pinhole open through the NAT providing that the router's NAT implementation is not substandard. Standard is roughly 30 seconds.

Only if the pinhole was to collapse prior 20 seconds could there be an issue with incoming calls since the router would not allow the source packets in.

Now for audio, on outbound calls, Vonage wont send any RTP packets to the Telephone adapter until the first packets from the telephone adapter arrive at Vonage. This is what opens the media ports for the session. On inbound calls this is slightly different but as long as the router does not flag the RTP packets as a DOS attack, which has nothing to do with NAT or port forwarding as this would be a firewall feature, there wont be a problem.

So to answer your question, with a standard NAT router, port forwarding is never needed. If the router has some firewall features such as SPI, DOS, and IDS, these may have to be adjusted if there should be issues with 1 way or no audio or call completion problems inound or out.

Posts: 1 · New Forum Member Joined: Mar 19, 2010 Posts: 1

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