Server 2008 R2 Falling Off Network

Question

At random times my Server 2008 R2 machine will disconnect from the network, causing AD, DNS, and DFS to failover to a 2003 R2 server.  It is not the network equipment as the other server is ok and we have already tried changing out the equipment. 
It will do it for like 30 seconds or so and then come back online, the lights never go off on the switch.
Its a Broadcom NIC. 
------------------- Reitzel Technology www.reitzeltechnology.com

Answer 1

There are multiple events showing that the NIC lost link connectivity. Are you sure that the NIC and the connectivity is fine?
Try using another addon NIC atleast for test.
Also recommend to resolve the DCOM permission issue for IPBusEnum using dcomcnfg.
Refer this article on how to change dcom permissions on w2k8r2
http://social.technet.microsoft.com/Forums/en-US/winservergen/thread/239741f3-1ce7-476b-88b0-860d5e1724d2/
Log Name:      System
Source:        b57nd60a
Date:          1/9/2012 12:07:10 AM
Event ID:      4
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      RTSRV.ReitzelTechnology.int
Description:
Broadcom NetXtreme Gigabit Ethernet: The network link is down.  Check to make sure the network cable is properly connected.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="b57nd60a" />
    <EventID Qualifiers="32773">4</EventID>
    <Level>3</Level>
    <Task>0</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2012-01-08T18:37:10.465526800Z" />
    <EventRecordID>27210</EventRecordID>
    <Channel>System</Channel>
    <Computer>RTSRV.ReitzelTechnology.int</Computer>
    <Security />
  </System>
  <EventData>
    <Data>\Device\NDMP13</Data>
    <Data>Broadcom NetXtreme Gigabit Ethernet</Data>
    <Binary>00000000020030000000000004000580000000000000000000000000000000000000000000000000</Binary>
  </EventData>
</Event>
Log Name:      System
Source:        Microsoft-Windows-DistributedCOM
Date:          1/8/2012 3:43:51 AM
Event ID:      10016
Task Category: None
Level:         Error
Keywords:      Classic
User:          SYSTEM
Computer:      RTSRV.ReitzelTechnology.int
Description:
The application-specific permission settings do not grant Local Launch permission for the COM Server application with CLSID
{C97FCC79-E628-407D-AE68-A06AD6D8B4D1}
 and APPID
{344ED43D-D086-4961-86A6-1106F4ACAD9B}
 to the user NT AUTHORITY\SYSTEM SID (S-1-5-18) from address LocalHost (Using LRPC). This security permission can be modified using the Component Services administrative tool.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-DistributedCOM" Guid="{1B562E86-B7AA-4131-BADC-B6F3A001407E}" EventSourceName="DCOM" />
    <EventID Qualifiers="49152">10016</EventID>
    <Version>0</Version>
    <Level>2</Level>
    <Task>0</Task>
    <Opcode>0</Opcode>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2012-01-07T22:13:51.000000000Z" />
    <EventRecordID>26728</EventRecordID>
    <Correlation />
    <Execution ProcessID="0" ThreadID="0" />
    <Channel>System</Channel>
    <Computer>RTSRV.ReitzelTechnology.int</Computer>
    <Security UserID="S-1-5-18" />
  </System>
  <EventData>
    <Data Name="param1">application-specific</Data>
    <Data Name="param2">Local</Data>
    <Data Name="param3">Launch</Data>
    <Data Name="param4">{C97FCC79-E628-407D-AE68-A06AD6D8B4D1}</Data>
    <Data Name="param5">{344ED43D-D086-4961-86A6-1106F4ACAD9B}</Data>
    <Data Name="param6">NT AUTHORITY</Data>
    <Data Name="param7">SYSTEM</Data>
    <Data Name="param8">S-1-5-18</Data>
    <Data Name="param9">LocalHost (Using LRPC)</Data>
  </EventData>
</Event>
Sumesh P - Microsoft Online Community Support