Understanding Chassis Cluster Dual Control Links

Dual control links, where two pairs of control link interfaces are connected between each device in a cluster, are supported for the SRX5000 and SRX3000 lines. Having two control links helps to avoid a possible single point of failure.

For the SRX5000 line, this functionality requires a second Routing Engine, as well as a second Switch Control Board (SCB) to house the Routing Engine, to be installed on each device in the cluster. The purpose of the second Routing Engine is only to initialize the switch on the SCB.

For the SRX3000 line, this functionality requires an SRX Clustering Module (SCM) to be installed on each device in the cluster. Although the SCM fits in the Routing Engine slot, it is not a Routing Engine. SRX3000 line devices do not support a second Routing Engine. The purpose of the SCM is to initialize the second control link.

Note: For the SRX5000 line, the second Routing Engine must be running JUNOS Release 10.0 or later. For the SRX3000 line, the cluster must be running JUNOS Release 10.2 or later (the SCM is not supported in earlier releases and might be incorrectly recognized).

The second Routing Engine, to be installed on SRX5000 line devices only, does not provide backup functionality. It does not need to be upgraded, even when there is a software upgrade of the master Routing Engine on the same node. Note the following:

• You cannot run the CLI or enter configuration mode on the second Routing Engine.
• You do not need to set the chassis ID and cluster ID on the second Routing Engine.
• You need only a console connection to the second Routing Engine. (A console connection is not needed unless you want to check that the second Routing Engine booted up or to upgrade a software image.)
• You cannot log in to the second Routing Engine from the master Routing Engine.

Note: As long as the first Routing Engine is installed (even if it is rebooting or failing), the second Routing Engine cannot take over the chassis mastership; that is, it cannot control all the hardware on the chassis. The second Routing Engine can only become the master when the master Routing Engine is not present.

Related Topics

• JUNOS Software Feature Support Reference for SRX Series and J Series Devices
• Understanding Chassis Cluster Control Links
• Connecting Dual Control Links for SRX Series Devices in a Chassis Cluster
• Upgrading the Second Routing Engine When Using Chassis Cluster Dual Control Links on SRX5600 and SRX5800 Devices
• Understanding Chassis Cluster Control Link Heartbeats
• Understanding Chassis Cluster Control Link Failure and Recovery
• Understanding the Chassis Cluster Control Plane