Cisco 3750G - Catalyst Integrated Wireless LAN Controller, Руководство по настройке

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5-5
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 5 Managing Switch Stacks
Understanding Switch Stacks
The Catalyst 3750 IP services image cryptographic image has a higher priority than the
Catalyst 3750 IP base image during the master switch election in a stack. However, when two or
more switches in the stack use different software images, such as the IP base image for Cisco IOS
Release 12.1(11)AX and the cryptographic IP services image for Cisco IOS Release 12.1(19)EA1
or later, the switch running the IP base image is selected as the stack master. This occurs because
the switch running the cryptographic IP services image takes 10 seconds longer to start than does
the switch running the IP base image. The switch running the IP services image is excluded from
the master election process that lasts 10 seconds. To avoid this problem, upgrade the switch running
the IP base image to a software release later than Cisco IOS Release 12.1(11)AX or manually start
the master switch and wait at least 8 seconds before starting the new member switch.
5. The switch with the longest system up-time.
6.
The switch with the lowest MAC address.
A stack master retains its role unless one of these events occurs:
•
The switch stack is reset.
*
• The stack master is removed from the switch stack.
•
The stack master is reset or powered off.
• The stack master has failed.
•
The switch stack membership is increased by adding powered-on standalone switches or switch
stacks.
*
In the events marked by an asterisk (*), the current stack master might be re-elected based on the listed
factors.
When you power on or reset an entire switch stack, some stack members might not participate in the
stack master election. Stack members that are powered on within the same 20-second time frame
participate in the stack master election and have a chance to become the stack master. Stack members
that are powered on after the 20-second time frame do not participate in this initial election and only
become stack members. All stack members participate in re-elections. For all powering considerations
that affect stack-master elections, see the “Switch Installation” chapter in the hardware installation
guide.
Note
Stack master elections occur over a 10-second time frame on switches running releases earlier than Cisco
IOS Release 12.2(20)SE3.
The new stack master becomes available after a few seconds. In the meantime, the switch stack uses the
forwarding tables in memory to minimize network disruption. The physical interfaces on the other
available stack members are not affected while a new stack master is elected and is resetting.
If a new stack master is elected and the previous stack master becomes available, the previous stack
master
does not resume its role as stack master.
As described in the hardware installation guide, you can use the Master LED on the switch to see if the
switch is the stack master.