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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 16 Configuring VTP
Understanding VTP
VTP Pruning
VTP pruning increases network available bandwidth by restricting flooded traffic to those trunk links
that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods
broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even
though receiving switches might discard them. VTP pruning is disabled by default.
VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the
p
runing-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 in all VTP versions.
Figure 16-1
shows a switched network without VTP pruning enabled. Port 1 on Switch A and Port 2 on
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 16-1 Flooding Traffic without VTP Pruning
Switch D
Switch E
Switch CSwitch F Switch A
Switch B
Port 1
Port 2
Red
VLAN
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