Specifications

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Cisco ME 3400 Ethernet Access Switch Command Reference
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Chapter 2 Cisco ME 3400 Ethernet Access Switch Cisco IOS Commands
switchport trunk
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), Link Aggregation Control Protocol
(LACP), Dynamic Trunking Protocol (DTP), and VLAN Trunking Protocol (VTP) in VLAN 1.
• The no form of the allowed vlan command resets the list to the default list, which allows all VLANs.
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
You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC
command.
Related Commands Command Description
show interfaces switchport Displays the administrative and operational status of a switching
(nonrouting) port, including port blocking and port protection settings.
switchport mode Configures the VLAN membership mode of a port.