5-5
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter 5 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 (for example, the command switch and member switches 8, 9, and 10 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 command
switch discovers them and adds them to the list of candidate switches.
Figure 5-1
shows a switch cluster with 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 3 hops from the edge of the cluster. It does not discover switch 15 because it
is 4 hops from the edge of the cluster.
Figure 5-1
Discovery through CDP Hops
Si
Catalyst 3550
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