Configuring WLBS Hosts When Directly Connected to a Layer 2 Switch

ID: Q232315


The information in this article applies to:


SUMMARY

For Windows Load Balancing Service (WLBS) to work properly, every packet directed to the virtual IP (VIP) address must reach all WLBS hosts. The WLBS host decides which packet to accept.


MORE INFORMATION

When the cluster network adapter of each WLBS host is connected to a port on a Layer 2 switch (the same switch) instead of a hub, the switch tries to learn the media access control (MAC) address of the computer connected to each of its ports so it can associate a port to a MAC address. Ethernet switches send frames to a MAC address using the port associated with the MAC address.

If a switch associates the cluster's MAC address to one of its ports, WLBS is unable to correctly load-balance traffic. There are two ways you can configure WLBS to prevent a switch from associating the cluster's MAC address:

When the local router needs to send a packet to the VIP, the local router uses address resolution protocol (ARP) to determine the VIP's MAC address.

WLBS replies to these ARP requests. When you mask the source MAC address, the ARP response from WLBS has a dummy source MAC address in the Ethernet frame, but contains the MAC address of the correct cluster in the ARP header.


REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base:

Q193601 Registry Parameters for Windows NT Load Balancing Service
Q193602 How to Use a Switch to Interconnect WLBS Cluster Hosts

Additional query words:


Keywords          : kbnetwork 
Version           : winnt:1.0,4.0
Platform          : winnt 
Issue type        : kbinfo 

Last Reviewed: May 27, 1999