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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 5 Clustering Switches
Understanding Switch Clusters
Understanding Switch Clusters
A switch cluster is a group of connected Catalyst switches that are managed as a single entity. In a switch
cluster, 1 switch must be the command switch andupto15switchescanbemember switches. The total
number of switches in a cluster cannot exceed 16 switches. The command switch is the single point of
access used to configure, manage, and monitor the member switches. Cluster members can belong to
only one cluster at a time.
The benefits of clustering switches include:
• Management of Catalyst switches regardless of their interconnection media and their physical
locations. The switches can be in the same location, or they can be distributed across a Layer 2
network. Cluster members are connected through the management VLAN of the command switch
according to the connectivity guidelines described in the “Automatic Discovery of Cluster
Candidates and Members” sectiononpage5-4.
• Command-switch redundancy if a command switch fails. One or more switches can be designated
as standby command switches to avoid loss of contact with cluster members. A cluster standby group
is a group of standby command switches.
• Management of a variety of Catalyst switches through a single IP address. This conserves on IP
addresses, especially if you have a limited number of them. All communication with the switch
cluster is through the command switch IP address.
For other clustering benefits, see the “Advantages of Using CMS and Clustering Switches” section on
page 1-7.
Refer to the release notes for the list of Catalyst switches eligible for switch clustering, including which
ones can be command switches and which ones can only be member switches, and the required software
versions.
Command Switch Characteristics
A Catalyst 2950 command switch must meet these requirements:
• It is running Cisco IOS Release 12.0(5.2)WC(1) or later.
• It has an IP address.
• It has Cisco Discovery Protocol (CDP) version 2 enabled (the default).
• Itisnotacommandormemberswitchofanothercluster.
• It is connected to the standby command switches and member switches through its management
VLAN.
• No access lists have been defined for the switch because access lists can restrict access to a switch.
Access lists are not usually used in configuring the switch, except for the CMP-NAT-ACL access
list that is created when a device is configured as the command switch.
Note • We strongly recommend that the highest-end, command-capable switch in the cluster be the
command switch:
• If your switch cluster has a Catalyst 3550 switch, that switch should be the command switch.
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