Directory Server 6.3 supports an unlimited number of masters in a multi-master topology. This and other changes might mean that you redesign your topology rather than migrate to an identical topology with new servers. See Part III, Logical Design, in Sun Java System Directory Server Enterprise Edition 6.3 Deployment Planning Guide before continuing.
When migrating replicated version 5 servers, you typically start with the consumers, continue with the hubs, and finish with the masters. This bottom-up approach involves interrupting only one server at a time, rather than interrupting an entire branch of the replication topology. The approach also helps you avoid potential custom schema synchronization issues between masters and consumers.