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Understanding Chassis Cluster Control Link Heartbeats

Junos OS transmits heartbeat signals over the control link at a configured interval. The system uses heartbeat transmissions to determine the “health” of the control link. If the number of missed heartbeats has reached the configured threshold, the system assesses whether a failure condition exists.

You specify the heartbeat threshold and heartbeat interval when you configure the chassis cluster .

The system monitors the control link's status by default.

For dual control links, which are supported on the SRX1400, SRX5600, SRX5800, and SRX3000 lines, the Juniper Services Redundancy Protocol process (jsrpd) sends and receives the control heartbeat messages on both control links. As long as heartbeats are received on one of the control links, Junos OS considers the other node to be alive.

The product of the heartbeat-threshold option and the heartbeat-interval option defines the wait time before failover is triggered. The default values of these options produce a wait time of 3 seconds. A heartbeat-threshold of 5 and a heartbeat-interval of 1000 milliseconds would yield a wait time of 5 seconds. Setting the heartbeat-threshold to 4 and the heartbeat-interval to 1250 milliseconds would also yield a wait time of 5 seconds.

In a chassis cluster environment, as the number of logical interfaces is scaled upward, the time before a failover is triggered needs to be increased accordingly. At maximum capacity on an SRX5400 or an SRX5600 or an SRX5800 device, we recommend that you increase the configured time before failover to at least 5 seconds. In a large chassis cluster configuration on an SRX3400 or SRX3600 device, we recommend increasing the wait to 8 seconds.

 

Related Documentation

 

Modified: 2016-10-23

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