Cisco WS-C4003 - Catalyst 4000 Chassis Switch Software Configuration Manual page 156

Understanding How VTP Works
Figure 9-1
Switch 6
Figure 9-2
Switch 1 is not forwarded to Switches 3, 5, and 6 because traffic for the Red VLAN has been pruned on
the links indicated (port 5 on Switch 2 and port 4 on Switch 4).
Figure 9-2
Flooded traffic
is pruned
Switch 6
Enabling VTP pruning on a VTP server enables pruning for the entire management domain. VTP pruning
takes effect several seconds after you enable it. By default, VLANs 2 through 1000 are pruning eligible.
VTP pruning does not prune traffic from VLANs that are pruning ineligible. VLAN 1 is always pruning
ineligible; traffic from VLAN 1 cannot be pruned.
To make a VLAN pruning ineligible, enter the clear vtp prunning command. To make a VLAN pruning
eligible again, enter the set vtp pruneeligible command. You can set VLAN pruning eligibility
regardless of whether VTP pruning is enabled or disabled for the domain. Pruning eligibility always
applies to the local device only, not for the entire VTP domain.
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
9-4
Flooding Traffic without VTP Pruning
Switch 4
Switch 5
Switch 3
shows the same switched network with VTP pruning enabled. The broadcast traffic from
Flooding Traffic with VTP Pruning
Switch 4
Port 2
Port
4
Switch 5
Port
5
Switch 3
Port 2
Switch 2
Red
VLAN
Port 1
Switch 1
Switch 2
Red
VLAN
Port 1
Switch 1
Chapter 9 Configuring VTP
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