[FW1] NetMeeting, VOIP and NAT

["Belanger, Derek" <DBelange@FW1-NOSPAMcomversens.com>]

FW: FW1 4.0
OS: NT 4.0
	
While setting up VOIP to be streamed to NetMeeting via NetMeeting services
and UDP>3100 I encounter a problem when using static NAT.

This is the problem:

1)	A "negotiation server" negotiates with the clients NetMeeting
application informing it to expect streaming from a different IP address
(the IP of the VOIP server). 
2)	The "negotiation server" also informs the client side NetMeeting
that, should it need to respond, it should direct packets to the VOIP
server, not the "negotiation server". 
3)	However streaming only works in one direction, from the server to
the client. When I sniff the session the VOIP server clearly sends the UDP
packets to the client. However when the client sends packets back it does
not send them to the VOIP server it sends them to the "negotiation server".
THIS DOES NOT HAPPEN IF THERE IS NO NAT! How can NAT cause this behavior? 

BTW both the "negotiation server" and the VOIP server are static NAT'ed
behind the same FW.

Please, if you have any information let me know...I don't even know where
start with this one.

Thanks,
--Derek



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