Configuring Native 802.1Q Vlans - Cisco Nexus 3000 Series Configuration Manual

Configuring Native 802.1Q VLANs

Procedure
Step 1
Step 2
Step 3
This example shows how to add VLANs to the list of allowed VLANs on an Ethernet trunk port:
switch# configure terminal
switch(config)# interface ethernet 1/3
switch(config-if)# switchport trunk allow vlan 15-20
Configuring Native 802.1Q VLANs
Typically, you configure 802.1Q trunks with a native VLAN ID, which strips tagging from all packets on that
VLAN. This configuration allows all untagged traffic and control traffic to transit the Cisco Nexus device.
Packets that enter the switch with 802.1Q tags that match the native VLAN ID value are similarly stripped
of tagging.
To maintain the tagging on the native VLAN and drop untagged traffic, enter the vlan dot1q tag native
command. The switch will tag the traffic received on the native VLAN and admit only 802.1Q-tagged frames,
dropping any untagged traffic, including untagged traffic in the native VLAN.
To maintain the tagging on the native VLAN and allow both tagged and untagged traffic, use the vlan dot1q
tag native tx-only command.
Control traffic continues to be accepted untagged on the native VLAN on a trunked port, even when the vlan
dot1q tag native command is enabled.
The vlan dot1q tag native command is enabled on global basis.
Note
Cisco Nexus 3000 Series NX-OS Layer 2 Switching Configuration Guide, Release 6.x
46
Command or Action
switch# configure terminal
switch(config)# interface {type
slot/port | port-channel number}
switch(config-if)# switchport trunk
allowed vlan {vlan-list all | none
[add |except | none | remove
{vlan-list}]}
Configuring Access and Trunk Interfaces
Purpose
Enters global configuration mode.
Specifies an interface to configure, and enters interface
configuration mode.
Sets allowed VLANs for the trunk interface. The default is
to allow all VLANs on the trunk interface: 1 to 3967 and
4048 to 4094. VLANs 3968 to 4047 are the default VLANs
reserved for internal use by default; this group of VLANs is
configurable. By default, all VLANs are allowed on all trunk
interfaces.
You cannot add internally allocated VLANs as
Note
allowed VLANs on trunk ports. The system returns
a message if you attempt to list an internally
allocated VLAN as an allowed VLAN.
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