[Asterisk-Users] SIP x NAT

César Davi Ávila do Nascimento cesard at intelbras.com.br
Mon Jan 31 06:37:16 MST 2005


Thanks a lot!

Regards

César

----- Original Message ----- 
From: "Rich Adamson" <radamson at routers.com>
To: "Asterisk Users Mailing List - Non-Commercial Discussion"
<asterisk-users at lists.digium.com>
Sent: Monday, January 31, 2005 9:18 AM
Subject: Re: [Asterisk-Users] SIP x NAT


> > I have a question for you:
> >
> > - "SIP doesn't work behind NAT very well"
> >
> > Do you agree with this sentence?
>
> Depends. Asterisk behind a nat box tends to be an implementation
> problem limited by the knowledge of the person doing the implementation
> and somewhat by the functionality implemented within the nat box.
>
> Sip phones behind a nat box (with asterisk on a registered IP address)
> tends to be rather easy, and how well it works depends a lot on how
> well the sip phone vendor implemented nat support.
>
> Both asterisk and sip phones behind different nat boxes tends to be
> the most difficult to implement and requires the greatest amount of
> knowledge/experience to implement. Again, depends a lot on the
> functionality provided in the nat boxes.
>
> The issue with sip is that session startup and control occurs across
> udp port 5060, and the two endpoints (* and phone) negotiate another
> set of udp ports for the rtp (voice) session. The choice of which rtp
> ports to use was left up to each sip phone vendor, so the udp port
> number in use could be anything from about 8000 (xlite) to something
> greater then 32,000.
>
> Some firewall/nat boxes will actually watch the sip rtp negotiation
> process by inspecting the contents of the sip packets, and open up the
> wanted ports. However, most cheap nat boxes don't do that, and leave
> it up to you to statically define/map the ports required.
>
>
> _______________________________________________
> Asterisk-Users mailing list
> Asterisk-Users at lists.digium.com
> http://lists.digium.com/mailman/listinfo/asterisk-users
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users
>




More information about the asterisk-users mailing list