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    Routing Engine, Host Module, and Host Subsystem Redundancy Connections

    It is important to understand how a redundant Routing Engine, redundant host module, or redundant subsystem communicates with its active counterparts to avoid severing the connection used for communication. Severing the connection can potentially trigger a failover protection.

    For example, the M160 router active host module (the Routing Engine and the MCS) has the running configuration on it and communicates with the MCS, which in turn communicates with the Flexible PIC Concentrator (FPC) and the Switching and Forwarding Modules (SFMs). The host modules send keepalive messages to each other, checking the operating state. Each host module issues keepalive responses, letting the other host module know that it is up and operating. If keepalive responses are not returned to the standby host module (response times will vary depending upon the time settings specified in the set chassis redundancy keepalive-time statement), the standby host module can become the active host module.

    You also can configure failover on the router to switch mastership if a critical process fails. If a critical process on the active host module terminates, the standby host module routing becomes the active host module. You can configure processes for which this should happen. For example, you can use the set interface-control failover other-routing-engine statement at the [edit system processes] hierarchy level to configure failover for the interface control daemon.

    Published: 2012-08-20