Chassis Cluster Redundancy Groups

Understanding Chassis Cluster Redundancy Group 0: Routing Engines

When you initialize a device in chassis cluster mode, the system creates a redundancy group referred to as redundancy group 0. Redundancy group 0 manages the primacy and failover between the Routing Engines on each node of the cluster. As is the case for all redundancy groups, redundancy group 0 can be primary on only one node at a time. The node on which redundancy group 0 is primary determines which Routing Engine is active in the cluster. A node is considered the primary node of the cluster if its Routing Engine is the active one.

The redundancy group 0 configuration specifies the priority for each node. The following priority scheme determines redundancy group 0 primacy. Note that the three-second value is the interval if the default heartbeat-threshold and heartbeat-interval values are used.

• The node that comes up first (at least three seconds prior to the other node) is the primary node.

• If both nodes come up at the same time (or within three seconds of each other):

  • The node with the higher configured priority is the primary node.

  • If there is a tie (either because the same value was configured or because default settings were used), the node with the lower node ID (node 0) is the primary node.

The previous priority scheme applies to redundancy groups x (redundancy groups numbered 1 through 128) as well, provided preempt is not configured. (See Example: Configuring Chassis Cluster Redundancy Groups.)

You cannot enable preemption for redundancy group 0. If you want to change the primary node for redundancy group 0, you must do a manual failover.

Be cautious and judicious in your use of redundancy group 0 manual failovers. A redundancy group 0 failover implies a Routing Engine failover, in which case all processes running on the primary node are killed and then spawned on the new primary Routing Engine. This failover could result in loss of state, such as routing state, and degrade performance by introducing system churn.

Understanding Chassis Cluster Redundancy Groups 1 Through 128

You can configure one or more redundancy groups numbered 1 through 128, referred to as redundancy group x. The maximum number of redundancy groups is equal to the number of redundant Ethernet interfaces that you configure (see Maximum Number of Redundant Ethernet Interfaces Allowed (SRX4100, SRX4200, SRX4600, SRX5400, SRX5600, SRX5800, SRX300, SRX320, SRX340, SRX345, SRX 380, and SRX1500)). Each redundancy group x acts as an independent unit of failover and is primary on only one node at a time.

Each redundancy group x contains one or more redundant Ethernet interfaces. A redundant Ethernet interface is a pseudo interface that contains at minimum a pair of physical Gigabit Ethernet interfaces or a pair of Fast Ethernet interfaces. If a redundancy group is active on node 0, then the child links of all the associated redundant Ethernet interfaces on node 0 are active. If the redundancy group fails over to node 1, then the child links of all redundant Ethernet interfaces on node 1 become active.

The following priority scheme determines redundancy group x primacy, provided preempt is not configured. If preempt is configured, the node with the higher priority is the primary node. Note that the three-second value is the interval if the default heartbeat-threshold and heartbeat-interval values are used.

• The node that comes up first (at least three seconds prior to the other node) is the primary node.

• If both nodes come up at the same time (or within three seconds of each other):

  • The node with the higher configured priority is the primary node.

  • If there is a tie (either because the same value was configured or because default settings were used), the node with the lower node ID (node 0) is the primary node.

On SRX Series chassis clusters, you can configure multiple redundancy groups to load-share traffic across the cluster. For example, you can configure some redundancy groups x to be primary on one node and some redundancy groups x to be primary on the other node. You can also configure a redundancy group x in a one-to-one relationship with a single redundant Ethernet interface to control which interface traffic flows through.

The traffic for a redundancy group is processed on the node where the redundancy group is active. Because more than one redundancy group can be configured, it is possible that the traffic from some redundancy groups is processed on one node while the traffic for other redundancy groups is processed on the other node (depending on where the redundancy group is active). Multiple redundancy groups make it possible for traffic to arrive over an ingress interface of one redundancy group and over an egress interface that belongs to another redundancy group. In this situation, the ingress and egress interfaces might not be active on the same node. When this happens, the traffic is forwarded over the fabric link to the appropriate node.

When you configure a redundancy group x, you must specify a priority for each node to determine the node on which the redundancy group x is primary. The node with the higher priority is selected as primary. The primacy of a redundancy group x can fail over from one node to the other. When a redundancy group x fails over to the other node, its redundant Ethernet interfaces on that node are active and their interfaces are passing traffic.

Table 1 gives an example of redundancy group x in an SRX Series chassis cluster and indicates the node on which the group is primary. It shows the redundant Ethernet interfaces and their interfaces configured for redundancy group x.

Some devices have both Gigabit Ethernet ports and Fast Ethernet ports.

As the example for a chassis cluster in Table 1 shows:

• The Routing Engine on node 0 is active because redundancy group 0 is primary on node 0. (The Routing Engine on node 1 is passive, serving as backup.)

• Redundancy group 1 is primary on node 0. Interfaces ge-1/0/0 and ge-1/3/0 belonging to redundant Ethernet interface 0 and redundant Ethernet interface 1 are active and handling traffic.

• Redundancy group 2 is primary on node 1. Interfaces ge-6/0/0 and ge-6/3/0 belonging to redundant Ethernet interface 2 and redundant Ethernet interface 3 are active and handling traffic.

• Redundancy group 3 is primary on node 0. Interfaces ge-3/0/0 and ge-3/3/0 belonging to redundant Ethernet interface 4 and redundant Ethernet interface 5 are active and handling traffic.