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Catalyst 3750 Switch Software Configuration Guide
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Chapter 6 Clustering Switches
Planning a Switch Cluster
Passwords
You do not need to assign passwords to an individual switch if it will be a cluster member. When a switch
joins a cluster, it inherits the command-switch password and retains it when it leaves the cluster. If no
command-switch password is configured, the cluster member switch inherits a null password. Cluster
member switches only inherit the command-switch password.
If you change the member-switch password to be different from the command-switch password and save
the change, the switch is not manageable by the cluster command switch until you change the
member-switch password to match the command-switch password. Rebooting the member switch does
not revert the password back to the command-switch password. We recommend that you do not change
the member-switch password after it joins a cluster.
For more information about passwords, see the “Preventing Unauthorized Access to Your Switch”
section on page 9-1.
For password considerations specific to the Catalyst 1900 and Catalyst 2820 switches, refer to the
installation and configuration guides for those switches.
SNMP Community Strings
A cluster member switch inherits the command-switch first read-only (RO) and read-write (RW)
community strings with @esN appended to the community strings:
• command-switch-readonly-community-string@esN, where N is the member-switch number.
• command-switch-readwrite-community-string@esN, where N is the member-switch number.
If the cluster command switch has multiple read-only or read-write community strings, only the first
read-only and read-write strings are propagated to the cluster member switch.
The switches support an unlimited number of community strings and string lengths. For more
information about SNMP and community strings, see Chapter 30, “Configuring SNMP.”
For SNMP considerations specific to the Catalyst 1900 and Catalyst 2820 switches, refer to the
installation and configuration guides specific to those switches.
Switch Clusters and Switch Stacks
A switch cluster can have one or more Catalyst 3750 switch stacks. Each switch stack can act as the
cluster command switch or as a single cluster member. Table 6-1 describes the basic differences between
switch stacks and switch clusters. For more information about switch stacks, see Chapter 5, “Managing
Switch Stacks.”
Table 6-1 Basic Comparison of Switch Stacks and Switch Clusters
Switch Stack Switch Cluster
Made up of Catalyst 3750 switches only Made up of cluster-capable switches, such as Catalyst 3750,
Catalyst 3550, and Catalyst 2950 switches
Stack members are connected through StackWise ports Cluster members are connected through LAN ports
Requires one stack master and supports up to eight other stack
members
Requires 1 cluster command switch and supports up to
15 other cluster member switches
Can be a cluster command switch or a cluster member switch Cannot be a stack master or stack member
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