[asterisk-dev] Multi-homed host routing problems with IAX

[Stephan A. Edelman]

Hello,

 

I'm not sure if this problem is being addressed or if it has even been
previously reported or discussed.

 

I have an Asterisk server with 5 different interfaces to 5 different
ISPs in our area. We have a number of users registering with the
Asterisk server from these various ISPs using ATAs. IAX registrations
work fine.

 

When calls are placed from these ATAs everything works as expected.
However, sending a call from Asterisk to one of these users results in a
CONGESTION, with the error "auto-congestion due to slow response".

 

Upon investigating, it appears that Asterisk originates all traffic from
the IP address associated with the first binaddr entry in the iax.conf
file (unless the ATA initiated the call).

 

Since most of the users are behind a Linksys, D-Link, etc. NAT
firewall/router, it is not going to have a port-mapping for this other
IP address and therefore the user's router will silently drop the IAX
call request, causing the auto-congestion.

 

When I switch the bind order in the iax.conf file, then I can get the
one user (who happens to send IAX registrations to that interface) to
receive incoming calls, but I break others.

 

For the moment, I'm NATing all 5 interfaces behind a NAT router and
doing a port-forward to the Asterisk server so it doesn't have to know
about these interfaces, but this requires another box and may cause a
limit on the number of simultaneous calls I can process due NAT
port-pair limitations.

 

I've looked through the code and do not see where Asterisk records the
interface address on which a particular packet was received. It would
make sense to me to record this so that a packet can be sent back from
the same interface.

 

Please let me know if this is a known issue and if there is any
development work on-going to address this. If not, I'm available to work
on this.

 

Regards,

 

Stephan.

--

Stephan A. Edelman, B.Eng.

NewAce Corporation

Toll Free: 1-877-463-9223 x221

International: +1 519 336 4837 x221 (Outside US & Canada)

Fax: +1 519 336 4046

Cell: +1 519 346 1581

 

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