[Asterisk-Dev] How IAX workd behind the firewall

Craig Southeren craigs at postincrement.com
Mon Jul 12 05:47:28 MST 2004

On Mon, 12 Jul 2004 07:28:18 -0600
Rich Adamson <radamson at routers.com> wrote:


> So, to answer the original poster's question, configuring a firewall
> for sip is much more difficult then iax mostly due to the need for
> multiple udp ports required for a sip session (that are selected based on 
> specific vendor implementations), verses a single udp port required
> for iax.

As far as I understand, that is absolutely correct. 

IAX requires a single random UDP port. 

SIP requires 2 adjacent UDP ports for RTP, plus 1 random UDP port for

H.323 requires 2 adjacent UDP ports for RTP, plus 1 random TCP port for


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