Specifications

12-5
Catalyst 2970 Switch Software Configuration Guide
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Chapter 12 Configuring VTP
Understanding VTP
Figure 12-1 Flooding Traffic without VTP Pruning
Figure 12-2 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 12-2 Optimized Flooded Traffic with VTP Pruning
Enabling VTP pruning on a VTP server enables pruning for the entire management domain. Making
VLANs pruning-eligible or pruning-ineligible affects pruning eligibility for those VLANs on that trunk
only (not on all switches in the VTP domain).
See the “Enabling VTP Pruning” section on page 12-13. VTP pruning takes effect several seconds after
you enable it. VTP pruning does not prune traffic from VLANs that are pruning-ineligible. VLAN 1 and
VLANs 1002 to 1005 are always pruning-ineligible; traffic from these VLANs cannot be pruned.
Extended-range VLANs (VLAN IDs higher than 1005) are also pruning-ineligible.
VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the
network are in VTP transparent mode, you should do one of these:
• Turn off VTP pruning in the entire network.
Switch D
Switch E
Switch CSwitch F Switch A
Switch B
Port 1
Port 2
Red
VLAN
89240
Switch D
Switch E
Switch CSwitch F Switch A
Switch B
Port 1
Port 2
Red
VLAN
89241
Port
4
Flooded traffic
is pruned.
Port
5
Flooded traffic
is pruned.