Hello there,we have an interesting poblem I wasn't able to solve so far.In our organisation are two w2k8 servers as DC running. The first (base x86) (so called fileserver) was PDC with DNS and fileservices. The second (x64) is used as mailserver with E2k7 and DNS, WINS. Replication, services, all running well so far.But:The updates are not working on the fileserver so i decided to reinstall the fileserver and change it also to x64 architecture.Thus, I wanted to transfer all FSMO roles and the global catalog to the mailserver, make it as master and PDC, demote the fileserver and safely remove it out of AD for new installation.The FSMO roles are already transferred, the mailserver is defined now as PDC.Last but not least, I wanted to transfer the global catalog function and - this doesn't work. Sure, I can mark the maileserver in the NTDS setting as catalog server and remove the attribute from the fileserver, but as soon as I turn off the fileserver, Exchange cannot find any global catalog server (which should be himself).I also examined the application log and found entries of the topology service MAD.EXE which stated, that the mailserver is not reachable (even though he can be seen in DNS entries, is pingable ..) but marked as global catalog.Maybe helpful is also the information from the E2k7 system configuration. There, for domaincontroller and global catalog server, only the fileserver can be seen . When global catalog is removed from fileserver, the field for global catalog in E2k7 remains empty.The log shows following: fileserver.xx.at CDG 1 7 7 1 0 1 1 7 1 mailserver.xx.at CDG 1 0 0 1 0 0 0 0 0We needurgently getting this problem solved as we need to install SQL server on the fileserver as MS doesnt allow MS Access connections from IIS7 anymore (and we have to reprogram our complete website and change to SQL - no idea,how all the thousands other users with the same problem solve that .. )I tried already to get some ideas in the W2k server forum but nobody there had any idea (even after examining the logs) so I was sent to this forum.Werner

Ok,we have found the solution by ourselve.The problem was caused by a deactivated IPv6 protocol. It MUST be ENABLED (even its not logical) otherwise, topology can't find the DC's...