Clustering and Load Balancing

In a clustered environment, traffic arriving via the primary and leaving an internal interface can appear to be blocked on the secondary if the destination is a broadcast or multicast address like those used for Microsoft Network Load Balancing. The traffic appears to be blocked on the internal interface of the secondary from a public IP address source. Capturing the traffic on the secondary and inspecting the destination address in Wireshark will reveal the nature of the destination MAC address.