Exchange 2010 fails to connect to Primary Domain Controller

My exchange 2010 server which is hosted on a virtual server 2008 R2 client, has lost connectivity to our domain controller/s and is failing over to the out of site domain controller.  Our primary domain controller is a physical box running server 2008 R2.  This is causing clients outlook to contantly disconnect and then reconnect to exchange and is limiting email functionality.  Below are the errors that I get every few seconds on the application logs of the exchange server:

Log Name:      Application
Source:        MSExchange ADAccess
Date:          9/4/2013 10:14:00 AM
Event ID:      2085
Task Category: Topology
Level:         Information
Keywords:      Classic
User:          N/A
Computer:      EMAIL1.aplsecurity.com
Description:
Process MSEXCHANGEADTOPOLOGYSERVICE.EXE (PID=8824). No Global Catalog server is up in the local site 'APL-Gilbert'. Exchange Active Directory Provider will use the following out of site global catalog servers:
DC3.aplsecurity.com
 
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="16388">2085</EventID>
    <Level>4</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-04T17:14:00.000000000Z" />
    <EventRecordID>552510</EventRecordID>
    <Channel>Application</Channel>
    <Computer>EMAIL1.aplsecurity.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>MSEXCHANGEADTOPOLOGYSERVICE.EXE</Data>
    <Data>8824</Data>
    <Data>APL-Gilbert</Data>
    <Data>DC3.aplsecurity.com
</Data>
  </EventData>
</Event>


Log Name:      Application
Source:        MSExchange ADAccess
Date:          9/4/2013 10:14:00 AM
Event ID:      2084
Task Category: Topology
Level:         Information
Keywords:      Classic
User:          N/A
Computer:      EMAIL1.aplsecurity.com
Description:
Process MSEXCHANGEADTOPOLOGYSERVICE.EXE (PID=8824). No Domain Controller server is up in the local site 'APL-Gilbert'. Exchange Active Directory Provider will use the following out of site Domain Controller servers:
DC3.aplsecurity.com
 
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="16388">2084</EventID>
    <Level>4</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-04T17:14:00.000000000Z" />
    <EventRecordID>552509</EventRecordID>
    <Channel>Application</Channel>
    <Computer>EMAIL1.aplsecurity.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>MSEXCHANGEADTOPOLOGYSERVICE.EXE</Data>
    <Data>8824</Data>
    <Data>APL-Gilbert</Data>
    <Data>DC3.aplsecurity.com
</Data>
  </EventData>
</Event>


Log Name:      Application
Source:        MSExchange ADAccess
Date:          9/4/2013 10:14:28 AM
Event ID:      2070
Task Category: Topology
Level:         Information
Keywords:      Classic
User:          N/A
Computer:      EMAIL1.aplsecurity.com
Description:
Process edgetransport.exe () (PID=2292).  Exchange Active Directory Provider lost contact with domain controller dc2.aplsecurity.com.  Error was 0x51 (ServerDown) (Active directory response: The LDAP server is unavailable.).  Exchange Active Directory Provider will attempt to reconnect with this domain controller when it is reachable.  
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="16388">2070</EventID>
    <Level>4</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-04T17:14:28.000000000Z" />
    <EventRecordID>552513</EventRecordID>
    <Channel>Application</Channel>
    <Computer>EMAIL1.aplsecurity.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>edgetransport.exe ()</Data>
    <Data>2292</Data>
    <Data>dc2.aplsecurity.com</Data>
    <Data>51</Data>
    <Data>Active directory response: The LDAP server is unavailable.</Data>
    <Data>ServerDown</Data>
  </EventData>
</Event>


Log Name:      Application
Source:        MSExchange ADAccess
Date:          9/4/2013 10:15:45 AM
Event ID:      2095
Task Category: Topology
Level:         Information
Keywords:      Classic
User:          N/A
Computer:      EMAIL1.aplsecurity.com
Description:
Process MSEXCHANGEADTOPOLOGYSERVICE.EXE (PID=8824). The Configuration Domain Controller has been changed from DC3.aplsecurity.com to dc1.aplsecurity.com.  
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="16388">2095</EventID>
    <Level>4</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-04T17:15:45.000000000Z" />
    <EventRecordID>552520</EventRecordID>
    <Channel>Application</Channel>
    <Computer>EMAIL1.aplsecurity.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>MSEXCHANGEADTOPOLOGYSERVICE.EXE</Data>
    <Data>8824</Data>
    <Data>DC3.aplsecurity.com</Data>
    <Data>dc1.aplsecurity.com</Data>
  </EventData>
</Event>


Log Name:      Application
Source:        MSExchange ADAccess
Date:          9/4/2013 10:15:48 AM
Event ID:      2070
Task Category: Topology
Level:         Information
Keywords:      Classic
User:          N/A
Computer:      EMAIL1.aplsecurity.com
Description:
Process Microsoft.Exchange.RpcClientAccess.Service.exe (PID=7360).  Exchange Active Directory Provider lost contact with domain controller dc1.aplsecurity.com.  Error was 0x51 (ServerDown) (Active directory response: The LDAP server is unavailable.).  Exchange Active Directory Provider will attempt to reconnect with this domain controller when it is reachable.  
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="16388">2070</EventID>
    <Level>4</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-04T17:15:48.000000000Z" />
    <EventRecordID>552521</EventRecordID>
    <Channel>Application</Channel>
    <Computer>EMAIL1.aplsecurity.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>Microsoft.Exchange.RpcClientAccess.Service.exe</Data>
    <Data>7360</Data>
    <Data>dc1.aplsecurity.com</Data>
    <Data>51</Data>
    <Data>Active directory response: The LDAP server is unavailable.</Data>
    <Data>ServerDown</Data>
  </EventData>
</Event>


Log Name:      Application
Source:        MSExchange ADAccess
Date:          9/4/2013 10:15:48 AM
Event ID:      2095
Task Category: Topology
Level:         Information
Keywords:      Classic
User:          N/A
Computer:      EMAIL1.aplsecurity.com
Description:
Process MSEXCHANGEADTOPOLOGYSERVICE.EXE (PID=8824). The Configuration Domain Controller has been changed from dc1.aplsecurity.com to DC4.aplsecurity.com.  
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="16388">2095</EventID>
    <Level>4</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-04T17:15:48.000000000Z" />
    <EventRecordID>552522</EventRecordID>
    <Channel>Application</Channel>
    <Computer>EMAIL1.aplsecurity.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>MSEXCHANGEADTOPOLOGYSERVICE.EXE</Data>
    <Data>8824</Data>
    <Data>dc1.aplsecurity.com</Data>
    <Data>DC4.aplsecurity.com</Data>
  </EventData>
</Event>


It just keeps trying to cycle through all of our 4 domain controllers until it ends up at DC3 which is our out of site domain controller??  I am able to connect to all of the DC's and don't see any errors that stand out to indicate that they are not working properly and they appear to be authenticating users to the network.  Please help!!
tbass81Asked:
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Adam FarageSr. Enterprise ArchitectCommented:
Check the NIC settings / update drivers on the Exchange server (CAS would be where this error is coming from) and also check the port settings / errors on the local switch.

It has to be a networking issue, as the errors above are saying there is a connectivity issue between Exchange and the DC.

You can also try cycling (restarting) the Exchange CAS in question (it might be an all in one server, not sure). It could just need a service restart for the AD Topology service and its dependants. But honestly, from the looks of your errors it seems this would be a networking issue (bad nic drivers, oversaturated virtual network / physical switch, bad switchport, ect).
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tbass81Author Commented:
It ended up being the quad port nic was bad that we had on our ESXi box.  When I moved the email and dc server to other vmnic's on a different physical nic the errors disappeared and everything started working normally.
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