Vtp Pruning - Cisco WS-C2955T-12 Software Manual

Using VTP

VTP Pruning

Pruning increases 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 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 on Catalyst 2900 XL and Catalyst 3500 XL trunk ports. If
the VLANs are configured as pruning-ineligible, the flooding continues. VTP pruning is also supported
with VTP version 1 and version 2.
Figure 8-3
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 8-3
Switch 5
Switch 6
Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
8-12
shows a switched network with VTP pruning enabled. The broadcast traffic from Switch 1 is
Optimized Flooded Traffic with VTP Pruning
Switch 4
Flooded traffic
Port
is pruned.
4
Flooded traffic
Port
is pruned.
5
Switch 3
Port 2
Catalyst 2900 XL or
Catalyst 3500 XL
Switch 2
Red
VLAN
Port 1
Switch 1
Chapter 8 Configuring VLANs
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