[Asterisk-Users] IAX and Firewall

[Rich Adamson]

> >VOIPJET - one of their servers was down, so switching the server IP
> >solved the problem.
> >Is it possible to specify two or three alternate server in iax.conf just
> >in case once goes down so the system will try alternate server
> >connection?
> >
> >  
> >
> Yes you can. The logic for cascading servers is in extensions.conf. 

You can't do it reliably as there are far too many reasons why a call
won't go through without giving you any usable indication why it
didn't go through.

If the itsp is simply not accessible (eg, down), that can be addressed.
But, if the itsp is having an issue completing the call (as one example
only), you  may or may not get anything back that is usable in decision
making within extensions.conf.

Other examples (real ones with teliax.com) include their system 
accepting a call from you and for whatever reason it simply isn't
processed (just hangs). Another is issues with codec selection on their 
part, and their upstream providers having issues.