Cisco Catalyst 4500 Series Software Configuration Manual page 625

Chapter 17 Configuring VLANs, VTP, and VMPS
Figure 17-2
Interface 2 on Switch 4 are assigned to the Red VLAN. A broadcast is sent from the host connected to
Switch 1. Switch 1 floods the broadcast and every network device in the network receives it, even though
Switches 3, 5, and 6 have no interfaces in the Red VLAN.
You can enable pruning globally on the Catalyst 4500 series switch (see the
section on page
Figure 17-2
Catalyst series
Catalyst series
switch 6
Figure 17-3
Switch 1 is not forwarded to Switches 3, 5, and 6 because traffic for the Red VLAN has been pruned on
the links indicated (Interface 5 on Switch 2 and Interface 4 on Switch 4).
Figure 17-3
Flooded traffic
is pruned.
Switch 5
Switch 6
Enabling VTP pruning on a VTP server enables pruning for the entire management domain. VTP pruning
takes effect several seconds after you enable it. By default, VLANs 2 through 1000 are eligible for
pruning. VTP pruning does not prune traffic from pruning-ineligible VLANs. VLAN 1 is always
ineligible for pruning; traffic from VLAN 1 cannot be pruned.
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
shows a switched network without VTP pruning enabled. Interface 1 on Switch 1 and
17-15).
Flooding Traffic without VTP Pruning
Catalyst series
switch 4
Catalyst series
switch 5
switch 2
Catalyst series Catalyst series
switch 3 switch 1
shows the same switched network with VTP pruning enabled. The broadcast traffic from
Flooding Traffic with VTP Pruning
Switch 4
Interface 2
Interface 4
Switch 2
Interface 5
Switch 3 Switch 1
Interface 2
Red
VLAN
Interface 1
Red
VLAN
Interface 1
VLAN Trunking Protocol
"Enabling VTP Pruning"
17-11