Cisco Systems 3750E manual Stack Master Election and Re-Election

Chapter 5 Managing Switch Stacks

Understanding Switch Stacks

Figure 5-2 Adding a Standalone Switch to a Switch Stack

Stack member 1

Stack member 2 and stack master

Stack member 3

Stack member 1

Stack member 1

Stack member 2 and stack master

Stack member 3

Stack member 4

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Stack Master Election and Re-Election

The stack master is elected or re-elected based on one of these factors and in the order listed:

1.The switch that is currently the stack master.

2.The switch with the highest stack member priority value.

Note We recommend assigning the highest priority value to the switch that you prefer to be the stack master. This ensures that the switch is re-elected as stack master if a re-election occurs.

3.The switch that is not using the default interface-level configuration.

4.The switch with the higher priority feature set and software image combination. These combinations are listed from highest to lowest priority:

–Advanced IP services feature set and the cryptographic universal software image

–Advanced IP services feature set and the noncryptographic software image

–IP services feature set and the cryptographic software image

–IP services feature set and the noncryptographic software image

–IP base feature set and the cryptographic software image

–IP base feature set and the noncryptographic software image

During the stack master switch election, differences in start-up times between the feature sets determine the stack master. The switch with the shorter start-up time becomes the stack master.

For example, a switch running the IP services feature set and the cryptographic software image has a higher priority than the switch running the IP base feature set and the noncryptographic image, but the switch running the IP base feature set becomes the stack master because the other switch takes 10 seconds longer to start. To avoid this problem, upgrade the switch running the IP base feature set to same feature set and software image as the other switch, or manually start the master switch and wait at least 8 seconds before starting the new member switch that running the IP base feature set.

5.The switch with the longest system up-time.

6.The switch with the lowest MAC address.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 5-5