This can all be accomplished with standard bridge lines stacked one on top of the other with continue_on_fail set to the list of codes you wish to fail over with.  You would also want to set hangup_after_bridge=true.  Loopback should NEVER be used in this case.

http://wiki.freeswitch.org/wiki/Channel_Variables#continue_on_fail
http://wiki.freeswitch.org/wiki/Channel_Variables#hangup_after_bridge

/b

On Aug 11, 2009, at 9:46 AM, Phillip Jones wrote:

Thanks for the reply Brian.

I went through this fairly carefully with Mike Jerris - please see
http://www.nabble.com/Calling-Multiple-Destinations-with-Failover-td24877157.html

I am very open to any other mechanism that allows the calling multiple
destinations with carrier failover support. I would have thought this
is a fairly common requirement and is a fundamental requirement in my
application.

As always - your help is appreciated.