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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 6 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
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.
, the command switch has ports assigned to VLANs 16 and 62. The CDP hop count is three.
The 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 6-1
Discovery through CDP Hops
Discovery through Non-CDP-Capable and Noncluster-Capable Devices
If a command switch is connected to a non-CDP-capable third-party hub (such as a non-Cisco hub), it
can discover cluster-enabled devices connected to that third-party hub. However, if the command switch
is connected to a noncluster-capable Cisco device, it cannot discover a cluster-enabled device connected
beyond the noncluster-capable Cisco device.
shows that the command switch discovers the Catalyst 3500 XL switch, which is connected
to a third-party hub. However, the command switch does not discover the Catalyst 3550 switch that is
connected to a Catalyst 5000 switch.
Refer to the release notes for the Catalyst switches that can be part of a switch cluster.
Si
Command switch
Member
switch 10
Member
switch 8
Member
switch 9
VLAN 62
Edge of
cluster
VLAN 16
65582
Switch 11
candidate
switch
Candidate
switches
Switch 12
Switch 13
Switch 14
Switch 15