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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 7 Clustering Switches
Planning a Switch Cluster
Discovery through CDP Hops
By using CDP, a 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 member switches are
connected to the cluster and to candidate switches. For example, member switches 9 and 10 in Figure 7-1
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 command
switch discovers them and adds them to the list of candidate switches.
In Figure 7-1, the non-LRE Catalyst 2950 command switch is running a release earlier than Cisco IOS
Release 12.1(9)EA1 and has ports assigned to management VLAN 16. In Figure 7-2, the non-LRE
Catalyst 2950 command switch is running Cisco IOS Release 12.1(9)EA1 or later and has ports assigned
to VLANs 16 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 four hops from the edge of the cluster.
Figure 7-1 Discovery through CDP Hops (Non-LRE Catalyst 2950 Command Switch Running a
Release Earlier than Cisco IOS Release 12.1(9)EA1)
Command switch
Member
switch 10
Edge of
cluster
Member
switch 8
Member
switch 9
Switch 11
candidate
switch
Candidate
switches
Management
VLAN 16
Management
VLAN 16
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Switch 12
Switch 13
Switch 14
Switch 15