[asterisk-users] asterisk to asterisk DID extentions

[Matt]

We have two * boxen linked with an IAX trunk they are on different networks.

Calling from any ext to any other remote ext on either box works 
fine.Outgoing calls from either box also works fine.

Problem when dialing in from DID (SIP or IAX provider) number, the 
caller cant transfer to any ext that is not on the local box.

How can I make * aware of the other ext on the remote box so the DID 
caller can access them like he can with the local box?

local ext are 8xx remote ext are 9xx

thanks

-Matt