[Asterisk-Users] Snom 200

[Christian Stredicke]

In Asterisk, that should be easy (I don't know if it is already done). The
trick is called "symmetrical NAT":

The Asterisk essentially ignored the media address of the SDP and waits for
the first RTP packet. It then just sends outgoing RTP to the address seen in
the incoming RTP packet.

Asterisk has the "advantage" that it does not try peer-to-peer RTP between
the user-agents. If the Asterisk is running on a globally routable address,
the symmetrical RTP trick is always possible, even if you have symmetrical
NAT.

The snom will allocate a port if you give it a STUN server. The STUN server
will have the address _stun._udp.<your-domain> (see RFC3489). If this server
is present, it will do its best to allocate a port on its own.

Christian

> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com [mailto:asterisk-users-
> admin at lists.digium.com] On Behalf Of Barry Fawthrop
> Sent: Monday, March 22, 2004 8:40 PM
> To: asterisk-users at lists.digium.com
> Subject: Re: [Asterisk-Users] Snom 200
> 
> Progress
> 
> It seems I can't hear the Say Time, due to RTP Double NAT
> I'm guess this is both problem 1 and 2 really issue.
> 
> My config:
> IP Phone <-> Router (Nat) <-> Internet <-> Linux (NAT) <-> * Server
> 
> ANyone know of work arounds the double NAT? or other methods
> to route RTP with snom 200s, to work around this?
> 
> Thanks in advance
> 
> Barry
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