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Cisco ME 3800X and ME 3600X Switch Command Reference
OL-28238-01
Chapter
switchport trunk
Command History
Usage Guidelines Native VLANs:
• All untagged traffic received on an IEEE 802.1Q trunk port is forwarded with the native VLAN
configured for the port.
• If a packet has a VLAN ID that is the same as the sending-port native VLAN ID, the packet is sent
without a tag; otherwise, the switch sends the packet with a tag.
• The no form of the native vlan command resets the native mode VLAN to the appropriate default
VLAN for the device.
Allowed VLAN:
• To reduce the risk of spanning-tree loops or storms, you can disable VLAN 1 on any individual
VLAN trunk port by removing VLAN 1 from the allowed list. When you remove VLAN 1 from a
trunk port, the interface continues to send and receive management traffic, for example, Cisco
Discovery Protocol (CDP), Port Aggregation Protocol (PAgP), and Link Aggregation Control
Protocol (LACP) in VLAN 1.
• The no form of the allowed vlan command resets the list to the default list, which allows all VLANs.
You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC
command.
Examples This example shows how to configure VLAN 3 as the default for the port to send all untagged traffic:
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport trunk native vlan 3
This example shows how to add VLANs 1, 2, 5, and 6 to the allowed list:
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport trunk allowed vlan add 1,2,5,6
Related Commands
Release Modification
12.2(52)EY This command was introduced.
Command Description
show interfaces switchport Displays the administrative and operational status of a switching
(nonrouting) port.
switchport mode Configures the VLAN membership mode of a port.
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