Dear All,

We have Exchange server 2013 it's working fine somw time from events i gt it 2070 AD .. But my domain controller it's working fine and ping and file sharing it's good .. what is the problem ? 

Process Microsoft.Exchange.Directory.TopologyService.exe (PID=2472).  Exchange Active Directory Provider lost contact with domain controller Main-Domain-Pr.KIMB.COM.  Error was 0x51 (ServerDown) (Active directory response: The server is unavailable.).  Exchange Active Directory Provider will attempt to reconnect with this domain controller when it is reachable.  

Unable to contact the active directory. Inner Exception System.DirectoryServices.ActiveDirectory.ActiveDirectoryServerDownException: The directory service is unavailable.

Name: "KIMB.COM"
 ---> System.Runtime.InteropServices.COMException: The directory service is unavailable.

   at System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail)
   at System.DirectoryServices.DirectoryEntry.Bind()
   at System.DirectoryServices.DirectoryEntry.get_AdsObject()
   at System.DirectoryServices.PropertyValueCollection.PopulateList()
   at System.DirectoryServices.PropertyValueCollection..ctor(DirectoryEntry entry, String propertyName)
   at System.DirectoryServices.PropertyCollection.get_Item(String propertyName)
   at System.DirectoryServices.ActiveDirectory.PropertyManager.GetPropertyValue(DirectoryContext context, DirectoryEntry directoryEntry, String propertyName)
   --- End of inner exception stack trace ---
   at System.DirectoryServices.ActiveDirectory.PropertyManager.GetPropertyValue(DirectoryContext context, DirectoryEntry directoryEntry, String propertyName)
   at System.DirectoryServices.ActiveDirectory.Forest.GetForest(DirectoryContext context)

Do you have any DC's in your environment that have not been demoted properly? Do you have multiple DC's in the site where Exchange is hosted to ensure that there is enough resources for your users.

I also suggest you check and ensure DNS is correct as well. Also check your SRV records in the DNS console (_msdcs.domain.com folder).

ALso take a look at the following TechNet for additional details for this specific error message.

https://technet.microsoft.com/en-us/library/bb217566(v=exchg.80).aspx

Will.

Dear Boss thanks for replay ,

Yes boss your are correct  I have Two DC one for Site "A" another one site "B" Last week we had some issue in site B so i did demoted site "B"  DC now only we have Site "A" DC and also i created additional domain in Site "A" both DC are replicated is well and working fine .. 

About Exchange 2013 we installed Site "A" and I login trough exchange  every time through domain\Administrator user with password and Exchange management ECP ..

As per your comment i have verified from DNS  msdcs FQDN ( one of the my domain controller IP unknown ) after that i added ... we will see if any error i will replay to you as soon as possible ... 

Hi,

Have you seen any error during the degraded process?

Are your exchange working fine?
Are you seeing any related errors in the event viewer of the Exchange server?
Please post the detailed error event information here for further analysis.

Regards,

David 

Hi,

Have you seen any error during the degraded process?

Are your exchange working fine?
Are you seeing any related errors in the event viewer of the Exchange server?
Please post the detailed error event information here for further analysis.

Regards,

David 

• Marked as answer by Suriya Subash 15 hours 37 minutes ago

Dear Boss,

Thanks for your support again same error appear but my exchange is working fine ... is there any big issue ? or how can solve this issue permanently... please could you save me..

Best Regards

Subash