Redundancy Group 0: Routing Engines

When you initialize a device in chassis cluster mode, the system creates a redundancy group referred to in this chapter 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. Below is how redundancy group 0 primacy is determined. Note that the three seconds 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.
• 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.
  • If there is a tie (either because same value was configured or because default settings were used), the node with the lower node ID (node 0) is the primary..

The above priority scheme applies to redundancy groups x as well, provided preempt is not configured.

Note: In addition to redundancy group 0, on J-series chassis clusters you configure other redundancy groups that manage the interfaces of the cluster nodes (only one such redundancy group is supported on SRX-series chassis clusters).

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.

Caution: 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.

Copyright © 2009, Juniper Networks, Inc. All rights reserved. Trademark Notice.