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    Understanding Chassis Cluster Redundancy Group Interface Monitoring

    For a redundancy group to automatically failover to another node, its interfaces must be monitored. When you configure a redundancy group, you can specify a set of interfaces that the redundancy group is to monitor for status (or “health”) to determine whether the interface is up or down. A monitored interface can be a child interface of any of its redundant Ethernet interfaces. When you configure an interface for a redundancy group to monitor, you give it a weight.

    Every redundancy group has a threshold tolerance value initially set to 255. When an interface monitored by a redundancy group becomes unavailable, its weight is subtracted from the redundancy group's threshold. When a redundancy group's threshold reaches 0, it fails over to the other node. For example, if redundancy group 1 was primary on node 0, on the threshold-crossing event, redundancy group 1 becomes primary on node 1. In this case, all the child interfaces of redundancy group 1's redundant Ethernet interfaces begin handling traffic.

    Note: Interface monitoring is not supported on Redundancy Group 0 (RG0) for SRX Series branch devices.

    A redundancy group failover occurs because the cumulative weight of the redundancy group's monitored interfaces has brought its threshold value to 0. When the monitored interfaces of a redundancy group on both nodes reach their thresholds at the same time, the redundancy group is primary on the node with the lower node ID, in this case node 0.

    • If you want to dampen the failovers occurring because of interface monitoring failures, use the hold-down-interval statement.
    • If a failover occurs on Redundancy Group 0 (RG0), the interface monitoring on the RG0 secondary is disabled for 30 seconds. This prevents failover of other redundancy groups along with RG0 failover.
     

    Related Documentation

     

    Published: 2012-06-29

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