Cisco Catalyst 2950 Software Configuration Manual page 367

Chapter 17 Configuring VTP
VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the
pruning-eligible list. Only VLANs included in the pruning-eligible list can be pruned. By default,
VLANs 2 through 1001 are pruning eligible switch trunk ports. If the VLANs are configured as
pruning-ineligible, the flooding continues. VTP pruning is supported with VTP version 1 and version 2.
Figure 17-1
Switch D are assigned to the Red VLAN. If a broadcast is sent from the host connected to Switch A,
Switch A floods the broadcast and every switch in the network receives it, even though Switches C, E,
and F have no ports in the Red VLAN.
Figure 17-1
Switch F
Figure 17-2
is not forwarded to Switches C, E, and F because traffic for the Red VLAN has been pruned on the links
shown (Port 5 on Switch B and Port 4 on Switch D).
Figure 17-2
Flooded traffic
is pruned.
Switch E
Switch F
78-11380-12
shows a switched network without VTP pruning enabled. Port 1 on Switch A and Port 2 on
Flooding Traffic without VTP Pruning
Switch D
Switch E
Switch B
Switch C
shows a switched network with VTP pruning enabled. The broadcast traffic from Switch A
Optimized Flooded Traffic with VTP Pruning
Switch D
Port 2
Port
4
Switch B
Flooded traffic
Port
is pruned.
5
Switch C
Port 2
Red
VLAN
Port 1
Switch A
Red
VLAN
Port 1
Switch A
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
Understanding VTP
17-5