Understanding the causes of failover
The following events can cause failover in a high availability configuration:
- If the secondary node does not receive a heartbeat packet from the primary node for a period of time that exceeds the dead interval set on the secondary. For more information about setting the dead interval, see Configuring Communication Intervals. Possible causes for a node not receiving heartbeat packets from a peer node include:
- A network configuration problem prevents heartbeats from traversing the network between the high availability nodes.
- The peer node experiences a hardware or software failure that causes it to freeze (hang), reboot, or otherwise stop processing and forwarding heartbeat packets.
- The primary node experiences a hardware failure of its SSL card.
- The primary node does not receive any heartbeat packets on its network interfaces for three seconds.
- On the primary node, a network interface that is not part of a Failover Interface Set (FIS) or a Link Aggregation (LA) channel and has the high availability Monitor (HAMON) enabled, fails. The interfaces are enabled, but go to a DOWN state.
- On the primary node, all interfaces in an FIS fail. The interfaces are enabled, but go to a DOWN state.
- On the primary node, an LA channel with HAMON enabled fails. The interfaces are enabled, but go to a DOWN state.
- On the primary node, all interfaces fail. In this case, failover occurs regardless of the HAMON configuration.
- On the primary node, all interfaces are manually disabled. In this case, failover occurs regardless of the HAMON configuration.
- You force a failover by issuing the force failover command on either node.
- A route monitor that is bound to the primary node goes DOWN.