Setting up Trixbox for H323 <-> SIP telephony is not a straightforward procedure. There is basically only one source of information and that is the Trixbox forum. The people on this forum who have a working configuration all integrate a hardware H323 system (like cisco call manager) with the trixbox. We started out trying to directly connect our H323 extensions to the trixbox but this did not seem possible. As a solution we started working with an H323 gatekeeper to handle H323 functionality and let the Trixbox function as gateway. After playing around with the configuration of clients, gk and Trixbox we are able make SIP -> H323 call. We can let H323 -> SIP ring but as soon as it is picked up the call is terminated by the Trixbox. We can handle H323 -> H323 by the just the gatekeeper.
To have come this far we have had extensive help from one person on the Trixbox forum who has a large H323 and SIP network and we followed mostly his suggestions. What follows is the configuration of Trixbox, GnuGK gatekeeper and different H323 clients as we have it right now.
Several people on the forum advise to use trixbox 1.2.3 since they find ooh323 does not work on trixbox 2.0. They also use a very specific version of the asterisk add-ons.