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Intermittent Connectivity Errors

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Intermittent Connectivity Errors - 23.Apr.2010 9:04:37 AM   


Posts: 21
Joined: 29.Jul.2008
From: Cincinnati, OH
Status: offline
Hi there,
We have been experiencing intermittent connectivity issues with our Exchange Server for months now, and I can't turn up any solutions.

When the issues occur, the App Log reports that the Exchange server cannot contact DC's or Global Catalog Servers. However, our network connectivity is always fine and the DCs and GCSs are alway available--it's just that Exchange server can't see them. The errors always occur for about 10 minutes. There is no rhyme or reason as to when they occur. This could happen at any time of day, and no other servers report any errors. We are unable to send/receive mail for about three or four minutes during this time.

I could not turn up anything obvious with DNS, so I ran NetStat Agent 3.0 and noticed that every time before we receive the intermittent errors, Netstat always reports the following TCP events (the Remote Address that is specified for each of these events is our primary DC):

New SYN_SENT Microsoft.Exchange.Cluster.ReplayService.exe
Removed N/A Microsoft.Exchange.Cluster.ReplayService.exe
New SYN_SENT Microsoft.Exchange.ServiceHost.exe
Removed N/A Microsoft.Exchange.ServiceHost.exe

Netstat does report events from these two processes at other times, with no errors, but during those "non-error" times the status of the two processes is always "ESTABLISHED" or "CLOSE_WAIT." Whenever the status of these two processes is "SYN_SENT," we then receive our intermittent connectivity errors.

Does this sound like anything obvious?

Thank you so much for your help,
Jessica Ianiro
Post #: 1
FIX: Intermittent Connectivity Errors - 26.Apr.2010 3:20:48 PM   


Posts: 21
Joined: 29.Jul.2008
From: Cincinnati, OH
Status: offline
Hey there,
I am happy to report that we found the solution to this.
The problem was with our Symantec Endpoint Security. Early on in troubleshooting this I had disabled Endpoint on the Exchange server with no luck. But the problem ended up being with Endpoint on the Domain Controller. Apparently Endpoint on the DC thought that the Domain Controller was getting "attacked" by our Exchange server at random intervals. This would cause the Domain Controller to cut-off communication with the Exchange server for a brief period of time. Hence all of our errors. The strange thing was that the DC did not report any of this in its Event logs. We determined this was the cause by viewing a Endpoint "Attacks Over Time" firewall report.
So, to fix this, we told Endpoint that all communication between the Exchange server and the Domain Controller was OK. We haven't had our intermittent Exchange errors since.
Hope this can save someone else a lot of time and headache!

(in reply to jianiro)
Post #: 2

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