Cisco Systems 2950 Understanding Switch Clusters

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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter7 Clustering Switches
Understanding Switch Clusters
Understanding Switch Clusters
A switch cluster is a group of connected Catalyst switches that a re manage d as a sing le entity. In a switch
cluster, 1switch must be the command switch and up to 15 switches can be member switches. The total
number of switches in a cluster cannot exceed 16switches. 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 or
Layer 3 (if your cluster is using a Catalyst 3550 mult ilayer switc h as a Layer 3 router between the
Layer 2 switches in the cluster) network.
Cluster members are connected to the command switch according to the connectivity guidelines
described in the “Automatic Discovery of Cluster Candidates and Members” section on page 7-5.
•Command-switch redundancy if a command switch fails. One or more s witc he s can be de signat ed
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 co nserves o n 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 1-9.
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.
These sections describe:
•Command Switch Characteristics, page 7-3
•Standby Command Switch Characteristics, page 7-3
•Candidate Switch and Member Switch Characteristics, page 7-4