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Catalyst 2940 Switch Software Configuration Guide
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Chapter5 Clustering Switches
Planning a Switch Cluster
Following these connectivity guidelines ensures automatic discovery of the switch cluster, cluster
candidates, connected switch clusters, and neighboring e dge d evices:
•Discovery Through CDP Hops, page 5-4
•Discovery Through Non-CDP-Capable and Noncluster-Capable Devices, page 5-5
•Discovery Through the Same Management VLAN, page 5-5
•Discovery Through Different Management VLANs, page 5-6
•Discovery of Newly Installed Switches, page 5-7
Discovery Through CDP Hops
By using CDP, a command switch can discover switches up to sevenCDP hops away (the default is
threehops) from the edge of the cluster. The edge of the cluster is where the last member switches are
connected to the cluster and to candidate switches. For example, m ember switches 9 a nd10 in Figure 5-1
are at the edge of the cluster.
You can set the number of hops the command switch searches for candidate and member switches by
selecting Cluster> Hop Count. When new candidate switches are added to the network, the comman d
switch discovers them and adds them to the list of candidate switches.
In Figure5-1, the c ommand switch has ports assigned to VLANs16 and 62. The CDP hop count is three.
Each 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 fo ur ho ps fro m th e ed ge o f th e clus te r.
Figure5-1 Discovery Through CDP Hops
Command switch
Member
switch 10
Member
switch 8
Member
switch 9
VLAN 62
Edge of
cluster
VLAN 16
Switch 11
candidate
switch Candidate
switches
Switch 12
Switch 13
Switch 14
Switch 15
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