The Philippines customer that I talked about in my previous post has 2 different version of Sun Java System Directory Server running in their 3 sites - 5.1 and 5.2. The key point is it is a replication over the WAN which makes the configuration challenging.
I made a verification and found that over LAN, replication between 5.1 and 5.2 is supported.
However, do note the following if replication is over the WAN:
Multi-master replication (MMR) over Wide Area Networks (WAN) is a new feature of Sun ONE Directory Server 5.2 that will allow for MMR configurations across geographical boundaries in international, multiple data-center deployments.
Due to differences in protocol, multi-master replication over WAN is not backward compatible with previous releases of Directory Server. As a result, in a multi-master replication over WAN configuration, all Directory Server instances separated by a WAN must be 5.2 instances.
Imagine what will happen if I did not conduct the feasibility study ... I'll be banging my heads when I fly in on-site only to discover that I have under-quoted the effort ... Ha!