Hi,I have 8 domain controllers (Windows 2008)distributed among 3 different sites. Everything was working fine until recently.For the past few days, i have been getting the following errors and warnings on all of my DC's on afrequent basis (daily on some, longer on others)Events: 1925, 1311, 1566,1865 Source: ActiveDirectory_DomainServiceEvents: 4000, 4015, 4004 Source:DNS-Server-ServiceEvents: 13508, 13526,13562Source:NtFrsAt that point the AD stops working. The problems go away when i restart the servers. But the next day or the day after that,it reappear. There's no specific timing, it's justrandom.Let me clarify that nothing was changed. Everything was working fine for more than 4 months. Now all of a sudden, i am starting to have these issues.Any help would greatly be appreciated. Thanks in advance.Regards

still waiting for a reply. Thanks

hi there,all the above events is referring to replication problems, i would request you to please check a) if replication is working between the sites ( for event id 1925 )http://technet.microsoft.com/en-us/library/cc778061.aspxb) and KCC issues for 1311 errorshttp://technet.microsoft.com/en-us/library/cc736750.aspxc) Please do check if you have set your DNS server appropriately d) 268109 KB for solving 1566 event id even this error points me to KCC also additional linkhttp://www.experts-exchange.com/Networking/Microsoft_Network/Q_21844257.html ( this link is for windows 2003 , but it will be applicable for windows 2008 as far as architecture is concerned and not GUI perspective )and i feel there is potential DNS issue with which all the above services are failing which are inturn dependent on DNS for resolution.For troubleshooting NTFRS please follow the below linkhttp://technet.microsoft.com/en-us/library/bb727056.aspxhope this helps sainath Windows Driver Development

hi,thanks for the reply. i have already gone through those article, did all the tests.There seems to be no problem with the replication. btw the problem has not happened in the past two days. Hopefully eveything will stay this way.Still I couldn'tidentifythesourceof the problem. what caused it in the first place.btw the DNSis working fine.ThanksP.S.http://www.experts-exchange.com/Networking/Microsoft_Network/Q_21844257.htmlThe above link looks helpful. Too bad i cannot view the answers as I'm not the member.

any other suggestions?

Hi, If the issue is resolved on its own, the most likely reason would be intermittent network connectivity failures between these AD sites/DCs. Once the connectivity resumes we will not see these errors again. You can also review the following articles: Fixing Replication Connectivity Problems (Event ID 1925) http://technet.microsoft.com/en-us/library/cc780728.aspx Network connectivity problems can make it impossible for domain controllers to form replication partnerships. Various events and errors can indicate a problem with network connectivity that is preventing replication from occurring. Troubleshooting Event ID 1311: Knowledge Consistency Checker http://support.microsoft.com/kb/214745 Cause: This behavior can occur if the Knowledge Consistency Checker (KCC) has determined that a site has been orphaned from the replication topology. In addition to the articles above, the following articles are useful for troubleshooting AD replication issues: Troubleshooting replication http://technet.microsoft.com/en-us/library/cc755349.aspx How to troubleshoot Event ID 1311 messages on a Windows 2000 domain http://support.microsoft.com/kb/307593 Event ID 1925: Attempt to establish a replication link failed due to connectivity problem http://technet.microsoft.com/en-us/library/cc787129.aspx Event ID 1311 KCC Replication Path Computation http://technet.microsoft.com/en-us/library/cc756493.aspx Hope the information is helpful.

Thanks for the replies.Ibelieve i am having the same problem mentioned here:http://social.technet.microsoft.com/Forums/en-US/winserverDS/thread/205f05a5-c5e2-4e81-9685-1ab52e397f78