IBM 12.1(22)EA6 User Manual

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Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide

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Chapter 13 Configuring VTP

Understanding 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 13-1

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 13-1

Flooding Traffic without VTP Pruning

Figure 13-2

shows a switched network with VTP pruning enabled. The broadcast traffic from Switch A

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 13-2

Optimized Flooded Traffic with VTP Pruning

Switch D

Switch E

Switch C

Switch F

Switch A

Switch B

Port 1

Port 2

Red

VLAN

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