Configuring Native 802.1Q Vlans - Cisco Nexus 5000 Series Configuration Manual

Configuring Access and Trunk Interfaces
DETAILED STEPS
Command or Action
Step 1
switch# configure terminal
Step 2
switch(config)# interface {type slot/port |
port-channel number}
Step 3 switch(config-if)# switchport trunk allowed
vlan {vlan-list all | none [add |except | none
| remove {vlan-list}]}
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 5000 Series
switch. 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.
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.
Note The vlan dot1q tag native command is enabled on global basis.
SUMMARY STEPS
1. switch# configure terminal
2. switch(config)# vlan dot1q tag native
3. (Optional) switch(config)# no vlan dot1q tag native
4. (Optional) switch# show vlan dot1q tag native
Purpose
Enters 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 allowed VLANs
Note
on trunk ports. The system returns a message if you attempt to
list an internally allocated VLAN as an allowed VLAN.
Cisco Nexus 5000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)N1(1)
Configuring Native 802.1Q VLANs
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