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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 11 Configuring VLANs
Configuring VLAN Trunks
• 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 that your network is loop-free before disabling
spanning tree.
Default Layer 2 Ethernet Interface VLAN Configuration
Table 11-5 shows the default Layer 2 Ethernet interface VLAN configuration.
Configuring an Ethernet Interface as a Trunk Port
These sections contain this configuration information about trunk ports:
• Interaction with Other Features, page 11-16
• Defining the Allowed VLANs on a Trunk, page 11-17
• Configuring the Native VLAN for Untagged Traffic, page 11-19
• Configuring the Native VLAN for Untagged Traffic, page 11-19
Interaction with Other Features
Trunking interacts with other features in these ways:
• A trunk port cannot be a secure port.
• A trunk port cannot be a tunnel 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 that you entered to all ports in the group:
–
allowed-VLAN list.
–
STP port priority for each VLAN.
–
STP Port Fast setting.
Note STP is supported by default on NNIs, but must be enabled on ENIs. STP is not supported on
UNIs.
–
trunk status: if one port in a port group ceases to be a trunk, all ports cease to be trunks.
Ta ble 11-5 Default Layer 2 Ethernet Interface VLAN Configuration
Feature Default Setting
Interface mode switchport mode access
Allowed VLAN range VLANs 1 to 4094
Default VLAN (for access ports) VLAN 1
Native VLAN (for IEEE 802.1Q trunks) VLAN 1