Has anyone had a successful experience utilizing an external vendor supported IVR system with their FreePBX setup? If so, if you could please provide a resource on how to link the extension numbers to their box, I would be very greatful! 
A trunk usually works well for this purpose, one that matches the interface on the external IVR.
Asterisk supports at least a dozen channel types.
I have tried setting up a trunk two different ways. The only information the vendor provided was “you need to create a SIP trunk with 2 channels and assign a 10-digit phone number.” Our FreePBX systems see each other through an IAX trunk with parameters host, username, secret, type, qualify, and trunk defined under Peer Details and parameters secret, type, and context defined for User Details (no register string). So, I tried that using the IP assigned to the box on our VoIP VLAN, without a username or secret. I got two valid phone numbers from my telcom guy and had my router guy add the dial plan rules for them into our gateway (which is done for all our extensions). I then created the extensions in my FreePBX box. But, didn’t know how to tie the extension to the box other than entering the extensions under the manipulation rules of the trunk. Since that didn’t work, I then tried to create a SIP trunk with only Peer Details defined for host username, secret, and type. Since that didn’t work, I tried adding the two extensions under manipulation rules. Since that didn’t work, I added an outbound route with the two extensions to go to the IVR-test trunk. All I get is “the number you have dialed is not in service.” As far as “matching the interface on the external IVR,” I’m not clear what all is involved other than the IP and user name and password I use to logon to it from the console. I’ve been using the following Method 2 as a guide: http://www.freepbx.org/support/documentation/administration-guide/connecting-2-or-more-boxes. But, not having much luck. (grrrr)