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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 6 Clustering Switches
Planning a Switch Cluster
• IP Addresses, page 6-12
• Hostnames, page 6-12
• Passwords, page 6-12
• SNMP Community Strings, page 6-13
• TACACS+ and RADIUS, page 6-13
• LRE Profiles, page 6-13
• Catalyst 1900 and Catalyst 2820 CLI Considerations, page 6-14
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 23, “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 6-5
• Discovery Through Non-CDP-Capable and Noncluster-Capable Devices, page 6-6
• Discovery Through Different VLANs, page 6-7
• Discovery Through Different Management VLANs, page 6-7
• Discovery of Newly Installed Switches, page 6-8
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 6-1 are at the edge of the cluster.
In Figure 6-1, 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.