Split-Brain Condition

When the HA link is disconnected or when the Active and Standby Edges fail to communicate with each other, both Edges assume the Active role. As a result, both Edges start responding to ARP requests on their LAN interfaces. This causes LAN traffic to be forwarded to both Edges, which could result in a broadcast storm on the LAN.

Typically, LAN switches connected to the HA Edge pair LAN ports run the Spanning Tree Protocol to prevent loops which trigger broadcast storms in the network. In such a condition, the switch would block traffic to one or both Edges. However, doing so would cause a total loss of traffic through the Edge pair.

Important: On an Enhanced HA deployment (where there is no Layer 2 Switch connected to the Edge's WAN interfaces), connectivity to the Primary Gateway is a requirement for split-brain detection. More details on the split-brain detection functionality can be found in the section Split-Brain Detection and Prevention.