Juniper JUNOS OS 10.3 - SOFTWARE, Manual, Page: 1022 / 3946

A Virtual Chassis configuration must have at least three members in order to include a
linecard member.
•
In a preprovisioned configuration, you can explicitly configure a member with the role
of linecard, which makes it ineligible for functioning as a master or backup.
• In a configuration that is not preprovisioned, the members that are not selected as
master or backup function as linecard members of the Virtual Chassis configuration.
The selection of the master and backup is determined by the mastership priority value
and secondary factors in the master election algorithm.
Member Switch and Member ID
Each physically discrete EX4200 switch is a potential member of a Virtual Chassis
configuration. When an EX4200 switch is powered on, it receives a member ID that is
displayed on the front-panel LCD. If the switch is powered on as a standalone switch, its
member ID is always
0
. When the switch is interconnected with other EX4200 switches
in a Virtual Chassis configuration, its member ID (
0
through
9
) is assigned by the master
based on various factors, such as the order in which the switch was added to the Virtual
Chassis configuration. As each switch is added and powered on, it receives the next
available (unused) member ID.
If the Virtual Chassis configuration previously included a member switch and that member
was physically disconnected or removed from the Virtual Chassis configuration, its
member ID is not available for assignment as part of the standard sequential assignment
by the master. For example, you might have a Virtual Chassis configuration composed
of member 0, member 2, and member 3, because member 1 was removed. When you
add another member switch and power it on, the master assigns it as member 4. However,
you can use the request virtual-chassis renumber command to explicitly change the
member ID of the new member switch to use member ID 1.
The member ID distinguishes the member switches from one another. You use the member
ID:
•
To assign a mastership priority value to a member switch
•
To configure interfaces for a member switch (the function is similar to a slot number
on Juniper Networks routers)
• To apply some operational commands to a member switch
•
To display status or characteristics of a member switch
Mastership Priority
In a configuration that is not preprovisioned, you can designate the role (master, backup,
or linecard) that a member switch performs within the Virtual Chassis configuration by
configuring its mastership priority (from
1 to 255 ). The mastership priority value is the
factor with the highest precedence for selecting the master of the Virtual Chassis
configuration.
The default value for mastership priority is 128 . When an EX4200 switch is powered on,
it receives the default mastership priority value. Because it is the only member of the
Copyright © 2010, Juniper Networks, Inc. 926
Complete Software Guide for Junos
®
OS for EX Series Ethernet Switches, Release 10.3