no ports are open on firewall..how is this working??

Posts: 1 · New Forum Member Joined: Jun 02, 2005 Posts: 1

Hi there have a Vonage linksys RT31P2 on my home net behind a PIX. I know there are standard ports to open up from the i-net to the router but i have nothing open. I only allow outbound access out. Nothing from the initiating from the outside world is allowed thru. My question is how is this working. Does the router estabilish a session with Vonage servers and piggy back on this estabilished session? Just curious. Is there any downside to this? Everything is working fine, calls (in and out, vm, forwarding...)
Thanks,
--minnoce944

Posts: 55 · Posted: Wed Jun 01, 2005 11:37 pm Post subject:

Is the PIX uPnP (Universal Plug & Play) compatible?

If it is then the RT31P2 can "ask" the PIX to open the ports only for it.

Posts: 59 · Full Forum Member Joined: Dec 16, 2004 Posts: 59

All the connections are opened from inside your network, thus the PIX allows them. Actually, since we are talking about UDP protocol, "connections" is not quite accurate. But your phone is sending a message (REGISTER) to the Vonage server, and the Vonage server tells it to keep registering like every 40 seconds or so. That keeps that nat port binding to the internal address/port open on the PIX, so later when Vonage wants to send you a call they can send a UDP message (INVITE) in to that port. Your phone then starts sending audio packets, now from a separate UDP port. Similarly, Vonage sees the packets coming the nat'ed ip and port on the PIX and starts sending the incoming audio back to that port. Again the PIX lets it in to your adapter. That's basically what is going on.

Posts: 1 · New Forum Member Joined: Oct 03, 2005 Posts: 1

Is this a vonange recommended/supported solution? Eventhough the PIX xlates allow initiated traffic back in, should I specify ACL's to always allow specific service/ports inbound?