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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 6 Clustering Switches
Unders tan din g Switch Clusters

Understandin g Switch Clust ers

A switch cluster i s a group of connected C atalyst swit ches that a re manage d as a sing le entity. In a sw itch
cluster, 1 switch must be the command switch a nd up to 15 switch es can be member switches. The total
number of switches in a cluster cannot exceed 16 switches. The command switc h is the single point of
access used to configure, mana ge, and mon itor th e member switches. Cluster mem bers can be long to
only one cluster at a time.
The bene fits of cluster ing swit ches incl ude:
•Managem ent of Catalys t switches regardless of their inte rconne ction medi a and thei r physical
locations. The switches can be in the same location, or they can be distributed across a Layer 2 or
Layer 3 (if your cl uster is us ing a Cataly st 3550 m ultila yer switc h as a Layer 3 router betwee n the
Layer 2 switches in the cluster) network.
Cluster members are connected to the command switch according to the connectivity guidelines
describe d in t he “Automa tic Discovery of Cluster Candida tes and Mem bers” section on page 6-5.
•Command -swi tch redu ndancy i f a c omma nd switc h fail s. One or mo re s witc hes c an be desi gnat ed
as st andby com mand sw itches to avoid loss of contact with cluster members. A cluste r standby
group i s a grou p o f stan dby co mm an d swi tc hes .
•Managem ent of a variety of Ca talyst swit che s thr ough a single IP addr ess. T his 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 clus terin g benefits , see the “Advantages of Using CMS and Clustering Switches” section on
page 1-7.
Refer to the release notes for the list o f Catalyst switches e ligible for switch clustering , including whic h
ones can be command switches and which ones can only be member switches, and the required software
versions.
These sec tions descr ibe:
•Command Switch Characteristics, page 6-3
•Standby Command Sw itch Charac teristic s, page 6-3
•Candidat e Sw itch a nd Me mb er Sw it ch Ch ar act eri stics, page 6-4