Intercom

Hi,
I have an implementation of intercom with snom phones… and between internal phones it work very fine (with Page cmd).
The problem is in DUNDi configuration. Infact the intercom don’t work between phones dislocates in more asterisk servers!!
I think than the problem is in transcode SIP/IAX2 (SIP for internal & IAX2 for Asterisk to Asterisk connection).
Can you help me on this?
Thank ALL