Network Load Balancing (NLB) is a load balancing technology for server clustering developed on Microsoft Windows Server. NLB supports load sharing and redundancy among servers within a cluster. To implement fast failover, NLB requires that the switch forwards network traffic to one or all servers in the cluster. Each server filters out the unexpected traffic. For more information, see Configuring network infrastructure to support the NLB operation mode

NLB is used to spread incoming requests across as many as 32 servers. Currently, the NLB in ArubaOS-CX switch supports only IGMP multicast mode. The IGMP multicast mode sends the packets out of the ports which connect to the cluster members. Assign a static multicast MAC address within the Internet Assigned Numbers Authority (IANA) range to the cluster's virtual unicast IP address. The clustered servers send IGMP joins to the configured multicast cluster group. If IGMP snooping is enabled, the switch dynamically populates the IGMP snooping table with the clustered servers, which prevents unicast flooding.