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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Clustering Switches
Planning a Switch Cluster
• Passwords, page 1-14
• SNMP Community Strings, page 1-14
• Switch Clusters and Switch Stacks, page 1-14
• TACACS+ and RADIUS, page 1-16
• LRE Profiles, page 1-16
See the release notes for the list of Catalyst switches eligible for switch clustering, including which ones
can be cluster command switches and which ones can only be cluster member switches, and for the
required software versions and browser and Java plug-in configurations.
Automatic Discovery of Cluster Candidates and Members
The cluster command switch uses Cisco Discovery Protocol (CDP) to discover cluster member switches,
candidate switches, neighboring switch clusters, and edge devices across multiple VLANs and in star or
cascaded topologies.
Note Do not disable CDP on the cluster command switch, on cluster members, or on any cluster-capable
switches that you might want a cluster command switch to discover. For more information about CDP,
see Chapter 1, “Configuring CDP.”
Following these connectivity guidelines ensures automatic discovery of the switch cluster, cluster
candidates, connected switch clusters, and neighboring edge devices:
• Discovery Through CDP Hops, page 1-5
• Discovery Through Non-CDP-Capable and Noncluster-Capable Devices, page 1-6
• Discovery Through Different VLANs, page 1-7
• Discovery Through Different Management VLANs, page 1-7
• Discovery Through Routed Ports, page 1-8
• Discovery of Newly Installed Switches, page 1-9
Discovery Through CDP Hops
By using CDP, a cluster command switch can discover switches up to seven CDP hops away (the default
is three hops) from the edge of the cluster. The edge of the cluster is where the last cluster member
switches are connected to the cluster and to candidate switches. For example, cluster member switches 9
and 10 in Figure 1-1 are at the edge of the cluster.
In Figure 1-1, the cluster command switch has ports assigned to VLANs 16 and 62. The CDP hop count
is three. The cluster command switch discovers switches 11, 12, 13, and 14 because they are within three
hops from the edge of the cluster. It does not discover switch 15 because it is four hops from the edge of
the cluster.
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