Article ID: 227812 - View products that this article applies to.
This article was previously published under Q227812
When Windows Load Balancing Service (WLBS) hosts that are operating in Unicast mode are connected directly to a switch, WLBS hides the virtual media access control (MAC) address by default so that the switch does not map the MAC address to a port. This is necessary because traffic to the virtual IP (VIP) address must reach all WLBS cluster hosts.
As indicated in the WLBS configuration documentation, only TCP/IP should be bound to the virtual network adapter. If another protocol is bound to the virtual network adapter, the other protocol may send frames out through the network adapter, not giving the WLBS driver a chance to mask the virtual MAC address.
The Network Load Balancing (NLB) driver in Windows 2000 Advanced Server and Datacenter Server is implemented as a filter and other protocols are not able to bypass it. NLB is then able to mask the virtual MAC address.
For additional information, please click the article number below to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/193602/EN-US/ )Configuration Options for WLBS Hosts Connected to a Layer 2 Switches