[asterisk-users] Same provider - IAX sounds bad, SIP sounds great

[Eric Wieling]

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Alejandro Imass
Sent: Tuesday, February 28, 2012 10:29 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Same provider - IAX sounds bad, SIP sounds great

On Tue, Feb 28, 2012 at 8:28 PM, Carlos Alvarez <carlos at televolve.com> wrote:
> On Tue, Feb 28, 2012 at 6:14 PM, Alejandro Imass <ait at p2ee.org> wrote:
>> Please expand as to how you set-up a SIP ATA behind a common home 
>> router set-up, without port redirection and/or use of a SIP proxy 
>> and/or STUN server? Unless the ATA has some sort of magic (e.g. VPN
>> support) it _cannot_ be done.
>
> Go buy a WRT-54G or nearly any consumer-class router and just plug in 
> a SIP device.  Done.  It works.  We *never* work on customer routers 
> and very rarely have to tell them to reconfigure their router at all.

What you are saying seems impossible and makes no sense unless the router is assigning a public IP or is "SIP aware" and knows how to read the routing data contained inside the SIP packets, and none of the consumer routers are SIP aware AFAIK, especially not the WRT-54G.

The other option is that the SIP ATA has WAN and LAN ports and the SIP device is being assigned a public IP.

SIP does not NAT by itself because it can't, because there is no routing info, it's simply impossible.
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You (or more correctly your Asterisk or SIP/RTP proxy) will handle all of that NAT stuff for you.  The only time I've ever had issues with SIP and NAT is when the router tries to do SIP ALG while Asterisk is also trying to do NAT fixups.