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cliffordgormleyFlag for United States of America

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Using Network Load Balancing in unicast mode

Hi,
Windows Server 2003
Balancing 2 web servers using Network Load Balancing. (NLB) in Unicast Mode.
Hello,
If I load-balance two www servers using NLB in unicast mode, do I need a separate network adaptor on each NLB host to transmit NLB heartbeats between the two hosts?
I know that, in unicast mode, the MAC address associated with each host will be identical, so they will not be able to communicate with each other.  Thus I think that I need a separate NIC for heartbeat communication.  None of the Windows documentation that I read seemed to explicity state this.  In fact, I read that hearbeat communication must occur across the NLB cluster adaptors...how can this happen in unicast mode if all NLB hosts have the same mac address!?
Thanks
Cliff
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65td
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Yes the cluster will need a separate heart beat nic.
See the attached link for information on MAC address.

http://technet2.microsoft.com/windowsserver/en/library/aa15cdd3-7ac5-4846-904e-4ff282f8e7f11033.mspx?mfr=true
http://support.microsoft.com/kb/898867
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oBdA

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So I guess the heartbeats are not sent to the Unicast mac address; the heartbeat is sent to a broadcast mac address that all NLB hosts listen to.
Please confirm.
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oBdA

Yes; check KB232711: "When the Windows NT Load Balancing Service (WLBS) cluster is configured to use a unicast media access control (MAC) address, the heartbeat is sent to the Ethernet broadcast address, FFFFFFFFFFFF."