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Configuring VLAN Trunks
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Default Layer 2 Ethernet Interface VLAN Configuration
Table 13-5
Table 13-5
Feature
Interface mode
Allowed VLAN range
VLAN range eligible for pruning
Default VLAN (for access ports)
Native VLAN (for IEEE 802.1Q trunks) VLAN 1
Configuring an Ethernet Interface as a Trunk Port
Because trunk ports send and receive VTP advertisements, to use VTP you must ensure that at least one
trunk port is configured on the switch and that this trunk port is connected to the trunk port of a second
switch. Otherwise, the switch cannot receive any VTP advertisements.
These sections contain this configuration information:
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Interaction with Other Features
Trunking interacts with other features in these ways:
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Catalyst 2928 Switch Software Configuration Guide
13-14
Disabling spanning tree on the native VLAN of an IEEE 802.1Q trunk without disabling spanning
tree on every VLAN in the network can potentially cause spanning-tree loops. We recommend that
you leave spanning tree enabled on the native VLAN of an IEEE 802.1Q trunk or disable spanning
tree on every VLAN in the network. Make sure your network is loop-free before you disable
spanning tree.
shows the default Layer 2 Ethernet interface VLAN configuration.
Default Layer 2 Ethernet Interface VLAN Configuration
Interaction with Other Features, page 13-14
Defining the Allowed VLANs on a Trunk, page 13-16
Changing the Pruning-Eligible List, page 13-17
Configuring the Native VLAN for Untagged Traffic, page 13-17
A trunk port cannot be a secure port.
Trunk ports can be grouped into EtherChannel port groups, but all trunks in the group must have the
same configuration. When a group is first created, all ports follow the parameters set for the first
port to be added to the group. If you change the configuration of one of these parameters, the switch
propagates the setting you entered to all ports in the group:
allowed-VLAN list.
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–
STP port priority for each VLAN.
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STP Port Fast setting.
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trunk status: if one port in a port group ceases to be a trunk, all ports cease to be trunks.
Default Setting
switchport mode dynamic auto
VLANs 1 to 4094
VLANs 2 to 1001
VLAN 1
Chapter 13
Configuring VLANs
OL-23389-01
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Troubleshooting
