Network Load Balanced (NLB) Servers Configured for Multicast

Network load balancer or similar proprietary load balancing technologies, comprised of multiple physical machines responding to a single “virtual” IP address, expect the switch to flood its traffic to all ports on the destination VLAN. The flooded traffic uses the Extreme Networks device soft forwarding path, subject to it‘s rate limiters, instead of the device hardware forwarding path. This traffic will also compete for the slow path resources and the first packets from other new flows.

To force the virtual server packets to take a hardware switch path, configure a MAC address static entry in the Filter Database (FDB). On the S- and K-Series, if the destination MAC is multicast (the Group bit is set), use the set mac multicast command, optionally specifying a port-list that further scopes the flooding, to force the forwarding traffic to use the hardware path (see Multicast MAC Address VLAN Port Limit). The set mac multicast command is only supported on frames that ingress and egress on the same VLAN (switched frames).

On the 7100-Series, to optimally support NLB, the VLAN with the NLB servers should consist of only ports that are attached to the NLB servers. non-NLB servers on this VLAN will receive the multicast frames that are typically only meant for the NLB servers.

On the 7100-Series, configure the device for enhanced routing functionality by entering the set limit resource_profile router1 command.