Demystifying Junos' Chassis Cluster Configuration

In this blog post, we will delve into the world of Junos' Chassis Cluster Configuration, a critical topic for those studying for the JNCIS-ENT certification. This feature is a key component of Juniper Networks' high availability solution, providing redundancy and reliability in the event of a system failure.

What is a Chassis Cluster?

A Chassis Cluster is a high availability feature that allows two Juniper devices to operate as a single, logical device. This is achieved by connecting the two devices via a control link and a fabric link. The control link is used for control plane communication, while the fabric link is used for data plane communication.

Configuring a Chassis Cluster

Let's dive into the configuration process. For this example, we will use two SRX Series devices.

Step 1: Prepare the Devices

First, ensure that both devices are running the same Junos OS version. Then, reset them to factory-default configuration and reboot.

request system zeroize

Step 2: Set the Cluster ID and Node ID

On each device, set the cluster ID and node ID. The cluster ID must be the same on both devices, while the node ID must be unique.

On the first device:

set chassis cluster cluster-id 1 node 0 reboot

On the second device:

set chassis cluster cluster-id 1 node 1 reboot

Step 3: Configure the Redundancy Group

A Redundancy Group (RG) is a group of interfaces or services that failover together. Configure at least one RG on each device.

set chassis cluster redundancy-group 1 node 0 priority 100
set chassis cluster redundancy-group 1 node 1 priority 1

Step 4: Configure the Control Link and Fabric Link

The control link (fxp1) and fabric link (fab0 and fab1) are automatically created when the cluster is formed. Assign an IP address to the fxp1 interface on each device and connect them directly or through a switch.

set interfaces fxp1 unit 0 family inet address

For the fabric link, assign an interface to fab0 and fab1.

set interfaces ge-0/0/2 fabric-options member-interfaces ge-0/0/2
set interfaces ge-0/0/3 fabric-options member-interfaces ge-0/0/3

Step 5: Verify the Configuration

Use the following command to verify the cluster status:

show chassis cluster status


Understanding and configuring Junos' Chassis Cluster is a crucial skill for network engineers aiming for the JNCIS-ENT certification. This high availability feature ensures that your network remains operational even in the event of a system failure. Practice configuring a Chassis Cluster in a lab environment to gain hands-on experience and deepen your understanding.

Remember, the key to mastering any technical topic is consistent practice and continuous learning. Keep exploring, keep practicing, and you'll be well on your way to acing your JNCIS-ENT certification.

© Ben Jacobson.RSS