Stacking Introduction
©2008 Allied Telesis Inc. All rights reserved.
Software Version 5.2.1
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
64.7
Stack Formation
As mentioned previously, a VCS always contains a master plus a number of other stack
members. To be part of a stack, a switch must connect to other potential stack members via
dedicated stacking ports.
On the SwitchBlade
®
x908, at least one non XEM-STK must be installed in the switch before it
is able to participate as a stack member.
Once the switches have been physically connected to form a stack, powering all the members
on automatically sets off a number of processes that enable the stack members to detect the
presence of the other stack members and form themselves into a VCS.
Selecting the Master Stack Member
The stack members are able to select which switch will become the stack master. This selection
is based on two components, firstly the stack member’s priority setting, and secondly its MAC
address. For both components, the lower the number the higher the priority.
The master is the node with the lowest priority value, or if no priorities are configured, the
node with the lowest MAC address. When a stack member is initially booted, its priority value
defaults to 128.
The stack also assigns a Stack ID number to each stack member. You can change the stack ID
by using either the ID select button on the XEM-STK, or by using the
stack renumber
command on page 65.22
. Note that the Stack ID number plays no part in the selection of the
master stack member.
Caution
Once the stack is formed, each stack member’s configuration is associated with its stack ID
number. Pressing the
select
button on a XEM-STK will set its switch member to have stack ID 1,
and
it will acquire the configuration settings assigned to that particular ID nu
m
ber
. The other
switches in the stack will then realign their stack IDs according to the stack’s physical topology.
For example: In a three switch VCS, the stack might have the following settings:
■
switch A has stack ID1, and a port configuration that we will call, “Switch A config.”
■
switch B has stack ID2, and a port configuration that we will call, “Switch B config.”
■
switch C has stack ID3, and a port configuration that we will call “Switch C config.”
Pressing the select button on switch B will produce the following result:
■
switch A now has stack ID3, and the port configuration “Switch C config.”
■
switch B now has stack ID1, and the port configuration “Switch A config.”
■
switch C now has stack ID2, and the port configuration “Switch B config.”
If, in this example, you pressed the select button by mistake, you could revert to the previous
configuration by using the
stack renumber
command to reset switch A to have stack ID1.