- If VMs that has to be configured as part of a Microsoft Network Load Balancing (NLB) cluster set in Unicast mode, then VM port group must be configured to accept both the MAC address changes and forged transmits. Since these systems shares a common IP address and virtual MAC address.
- The Notify Switches option should be set to No when the port group has VMs using Microsoft Network Load Balancing (NLB) in Unicast mode.
- vMotion for unicast NLB virtual machines is not supported, since all the VMs must need to run on the same host.
- To use vMotion, on the NLB in Multicast mode the Notify Switches option must be set to Yes and the VMs can run on Multiple ESX host.
VMware recommends configuring the Microsoft NLB Cluster in the Multicast Mode, though the Unicast mode works fine. For the Unicast to work efficiently the above settings has to be done.
To further troubleshoot the issue, you may look into the following reference Links:
- Microsoft NLB not working properly in Unicast Mode (1556)
- Microsoft Network Load Balancing Multicast and Unicastoperation modes (1006580)
- Sample Configuration – Network Load Balancing (NLB)unicast mode configuration (1006778)
- Sample Configuration – Network Load Balancing (NLB)Multicast Mode Configuration (1006558)