Understanding Chassis Cluster Redundancy Group Failover

Chassis cluster employs a number of highly efficient failover mechanisms that promote high availability to increase your system's overall reliability and productivity.

A redundancy group is a collection of objects that fail over as a group. Each redundancy group monitors a set of objects (physical interfaces), and each monitored object is assigned a weight. Each redundancy group has an initial threshold of 255. When a monitored object fails, the weight of the object is subtracted from the threshold value of the redundancy group. When the threshold value reaches zero, the redundancy group fails over to the other node. As a result, all the objects associated with the redundancy group fail over as well. Graceful restart of the routing protocols enables the SRX Series device to minimize traffic disruption during a failover.

Because back-to-back redundancy group 0 failovers that occur too quickly can cause a cluster to exhibit unpredictable behavior, a dampening time between failovers is needed. On a failover, the previous primary node moves to the secondary-hold state and stays there until the hold-down interval expires, after which it moves to the secondary state.

The default dampening time is 300 seconds (5 minutes) for redundancy group 0 and is configurable to up to 1800 seconds with the hold-down-interval statement. Redundancy groups x (redundancy groups numbered 1 through 128) have a default dampening time of 1 second, with a range of 0 through 1800 seconds. The hold-down interval affects manual failovers, as well as automatic failovers associated with monitoring failures.

Understanding Chassis Cluster Redundancy Group Failover

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