Redundancy Group Interface Monitoring

For a redundancy group x to automatically fail over to another node, its interfaces must be monitored. When you configure a redundancy group x, you can specify a set of interfaces the redundancy group x 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 x to monitor, you give it a weight.

Every redundancy group x has a threshold tolerance value initially set to 255. When an interface monitored by a redundancy group x becomes unavailable, its weight is subtracted from the redundancy group x's threshold. When a redundancy group x'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.

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

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