12.2.2.3. Multicast load balancing

A simple load balancing solution is to assign a multicast MAC address to the Service IP. In this case the clients target the Service IP, and a hub or switch before the firewall hosts forwards all requests to the multicast MAC address, resulting in all nodes of the cluster receiving all packets sent to the Service IP. The IP addresses of the clients are distributed between the nodes using some logic (for example, one node serves only clients with odd, the other one clients with even IP addresses), and the packet filter of each node is configured to accept only the packets of the clients they are responsible for.

Note

It is important that if in such a scenario one of the nodes fails, the remaining nodes have to take over the clients served by the failed node. This can be accomplished for example by using Heartbeat resources.