Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual page 999

Backup Role
Linecard Role
Copyright © 2010, Juniper Networks, Inc.
Chapter 37: EX4200 Virtual Chassis—Overview, Components, and Configurations
When an EX4200 switch is powered on as a standalone switch, it is considered the master
member. In a multimember Virtual Chassis configuration, one member functions as the
master and a second member functions as the backup:
In a preprovisioned configuration, one of the two members assigned as
functions as the master member. The selection of which member assigned as
functions as master and which as backup is determined by the software
routing-engine
based on the master election algorithm. See "Understanding How the Master in an
EX4200 Virtual Chassis Is Elected" on page 898.
In a configuration that is not preprovisioned, the selection of the master and backup
is determined by the mastership priority value and secondary factors in the master
election algorithm.
The member that functions in the backup role in an EX4200 Virtual Chassis:
Maintains a state of readiness to take over the master role if the master fails.
Runs Junos OS for EX Series switches in a backup role.
Synchronizes with the master in terms of protocol states, forwarding tables, and so
forth, so that it is prepared to preserve routing information and maintain network
connectivity without disruption in case the master is unavailable.
You must have at least two member switches in an EX4200 Virtual Chassis configuration
in order to have a backup member.
In a preprovisioned configuration, one of the two members assigned as
functions in the backup role. The selection of which member assigned as
functions as master and which as backup is determined by the software based on the
master election algorithm. See "Understanding How the Master in an EX4200 Virtual
Chassis Is Elected" on page 898.
In a configuration that is not preprovisioned, the selection of the master and backup
is determined by the mastership priority value and secondary factors in the master
election algorithm.
A member that functions in the linecard role in an EX4200 Virtual Chassis:
Runs only a subset of Junos OS for EX Series switches.
Does not run the chassis control protocols.
Can detect certain error conditions (such as an unplugged cable) on any interfaces
that have been configured on it through the master.
An EX4200 Virtual Chassis configuration must have at least three members in order to
include a linecard member.
routing-engine
routing-engine
routing-engine
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