[Asterisk-Dev] IAX2 Native Transfer + NAT

Steven Sokol ssokol at sokol-associates.com
Mon Feb 9 08:44:49 MST 2004

> If I understood your comments correctly, that would be "port address
> translation"
> (or PAT) that got you. Part of the reason for that is IAX uses the exact
> same
> port number for both source and destination udp ports, therefore the
> firewall
> can only handle one iax session in its nat/pat tables.

Perhaps I am missing something, but I have had several sessions running
simultaneously before, all traversing the NAT router.  Here's my network:

[Client A     ]
[]-----                               ... To Net...
                    |                                   |
[Client B     ]     |                                   |
[]------     []--[Switch]--[Cable Modem]
                    |     [Linksys NAT]      |
[Client C     ]     |-----[]      |
[]------                        |
                    |                 [Asterisk Server]
[Client D     ]     |                 [    ]
[Additional Clients...]

I have had both calls between NATted clients (A-C, B-D, etc.) and
simultaneous calls between clients and outside numbers (A-iaxtel, B-iaxtel)
without any problem.  If the IAX2 protocol was limited to strictly one port,
it would not be able to pass more than one call through the Linksys.

What I am suggesting is that IAX2 become not only firewall/NAT friendly, but
NAT-aware in terms of establishing the audio portion of the call.



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