Joining two DCs to same forest?

1) I have not been able to successfully implement AD DC
replication on Win2K3 Enterprise. One rule that Ace
recently told me about was that both servers have to be on
the same forest. Exchange server 2003 is on both AD DC
servers. How can I go about joining both servers to the
same forest once they have been setup on separate forests?
They are each the only machines on their own forests.

2) If I have to remove Exchange and AD on either or both
servers, is there a reference doc on the removal process?
The server2 install appears to have fundamental problems
with being discovered across the net by server1.

Thanks,
Mike

Our purpose for this setup is a breadboard test setup for
Exchange data replication for remote site disaster
recovery. Unfortunately the replication software has
trouble linking the replication agents at either end. We
are fairly confident the software is not the major issue
here but that it is a network issue.

We have two Win2K3 Exchange servers both on Win2K3
Enterprise at two locations linked by 500 series Cisco PIX
firewalls.

Due to budget constraints and against Microsoft
recommendations both servers are also inside Domain
Controllers.

Site1 has an inside IP range of xxx.xxx.1.1-xxx.xxx.1.254
Site2 has an inside IP range of xxx.xxx.2.1-xxx.xxx.2.254

We have setup lmhosts and host files on each machine with
references to the opposite machine.

We are able to:
o Browse shares on the opposite machines through IE
o Ping the opposite machines by IP and by name

We performed the following RPC tests:

1) Net View run on Server1 fails to resolve Server2.
Net View run on Server2 fails to resolve Server1.
2) Edited LMHOSTS files for both machines
3) Net View run on Server1 resolves Server2.
Net View run on Server2 fails to resolve Server1.**
4) Validated that both RPC Locator and RPC Service
are running on both servers. Started Locator on
both and set to automatic start.
5) RMA service still fails to start on Server1
6) Event Viewer on Server2 successfully connects
to Server1. Event Viewer on Server1 successfully
connects to Server2.

Some History:
The two servers are not identical so we cannot
image them to insure the configurations are the
same.