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Chapter 11
Configuring VLANs
Configuring the Native VLAN for Untagged Traffic
A trunk port configured with IEEE 802.1Q tagging can receive both tagged and untagged traffic. By
default, the switch forwards untagged traffic in the native VLAN configured for the port. The native
VLAN is VLAN 1 by default.
The native VLAN can be assigned any VLAN ID.
Note
For information about IEEE 802.1Q configuration issues, see the
Considerations" section on page
Beginning in privileged EXEC mode, follow these steps to configure the native VLAN on an
IEEE 802.1Q trunk:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
no shutdown
Step 4
switchport trunk native vlan vlan-id
Step 5
end
Step 6
show interfaces interface-id switchport
Step 7
copy running-config startup-config
To return to the default native VLAN, VLAN 1, use the no switchport trunk native vlan interface
configuration command.
If a packet has a VLAN ID that is the same as the sending port native VLAN ID, the packet is sent
untagged; otherwise, the switch sends the packet with a tag.
Configuring Trunk Ports for Load Sharing
Load sharing divides the bandwidth supplied by parallel trunks that connect switches. To avoid loops,
STP normally blocks all but one parallel link between switches. Using load sharing, you divide the traffic
between the links according to the VLAN to which the traffic belongs.
You configure load sharing on NNI trunk ports by using STP port priorities or STP path costs. For load
sharing using STP port priorities, both load-sharing links must be connected to the same switch. For load
sharing using STP path costs, each load-sharing link can be connected to the same switch or to two
different switches. For more information about STP, see
78-17058-01
11-15.
Purpose
Enter global configuration mode.
Define the interface that is configured as the IEEE 802.1Q trunk, and
enter interface configuration mode.
Enable the port, if necessary. By default, UNIs are disabled and NNIs
are enabled.
Configure the VLAN that is sending and receiving untagged traffic
on the trunk port.
For vlan-id, the range is 1 to 4094.
Return to privileged EXEC mode.
Verify your entries in the Trunking Native Mode VLAN field.
(Optional) Save your entries in the configuration file.
Chapter 14, "Configuring STP."
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Configuring VLAN Trunks
"IEEE 802.1Q Configuration
11-19
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Troubleshooting
