Does any one know if you can do this?

I am migrating in a piece meal fashion (dont ask why I have to do this) a DDI range from an old mitel system to Lync.

Becasue the range is not continue I have things like

1,2,3,6,7,9 are extensions on Lync
4,5,8 are on mitel.

and I a have sonus box as the SBC. (there are also other systems around for specifice cases which is why we bothered with the sonus )

Rather than create lots of rule on the sonus to route the calls as this becomes a regex night mare what I want to do is say

calls coming in to the sonus to ext 1-10 from external route to Lync
calls coming in to sonus from lync to ext 1-10 route to mitel..

With the idea being that sonus will first send all calls to lync, if lync has a match it will handle the call but it not it will send the call back to the sonus, seems to block a call coming in one trunk from being sent out the same trunk.

Now I know this is good practice as common sence says why would you ever need to do this. In fact in routing we call this "split horzion, don't send a route back out the interface you learn it on.

But in this case it means a reduction in configuration and all i need to do is as long as the extension is configured on either mitel or Lync the call will reach it with out and changes.

So any ideas on how to allow hairpinning on trunks in Lync ?