Cisco Catalyst 3120 User Manual

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Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
OL-12247-01
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
S
witch F Switch A
Switch B
Port 1
Port 2
Red
VLAN
8
9240
Switch D
Switch E
Switch C
S
witch F Switch A
Switch B
Port 1
Port 2
Red
VLAN
8
9241
Port
4
Flooded traffic
is pruned.
Port
5
Flooded traffic
is pruned.

Cisco Catalyst 3120 Specifications

General

Brand	Cisco
Model	Catalyst 3120
Category	Switch
Language	English