Administrator Guide

Configuring Native VLANs
Traditionally, ports can be either untagged for membership to one VLAN or tagged for membership to multiple VLANs.
You must connect an untagged port to a VLAN-unaware station (one that does not understand VLAN tags), and you must
connect a tagged port to a VLAN-aware station (one that generates and understands VLAN tags).
Native VLAN support breaks this barrier so that you can connect a port to both VLAN-aware and VLAN-unaware stations. Such
ports are referred to as hybrid ports. Physical and port-channel interfaces may be hybrid ports.
Native VLAN is useful in deployments where a Layer 2 port can receive both tagged and untagged traffic on the same physical
port. The classic example is connecting a voice-over-IP (VOIP) phone and a PC to the same port of the switch. The VOIP phone
is configured to generate tagged packets (with VLAN = VOICE VLAN) and the attached PC generates untagged packets.
NOTE: When a hybrid port is untagged in a VLAN but it receives tagged traffic, all traffic is accepted.
NOTE: You cannot configure an existing switchport or port channel interface for Native VLAN. Interfaces must have no
other Layer 2 or Layer 3 configurations when using the portmode hybrid command or a message similar to this displays:
% Error: Port is in Layer-2 mode Te 5/6.
To configure a port so that it can be a member of an untagged and tagged VLANs, use the following commands.
1. Remove any Layer 2 or Layer 3 configurations from the interface.
INTERFACE mode
2. Configure the interface for Hybrid mode.
INTERFACE mode
portmode hybrid
3. Configure the interface for Switchport mode.
INTERFACE mode
switchport
4. Add the interface to a tagged or untagged VLAN.
VLAN INTERFACE mode
[tagged | untagged]
Creating a Port-Based VLAN
To configure a port-based VLAN, create the VLAN and then add physical interfaces or port channel (LAG) interfaces to the
VLAN.
NOTE: The Default VLAN (VLAN 1) is part of the system startup configuration and does not require configuration.
A VLAN is active only if the VLAN contains interfaces and those interfaces are operationally up. As shown in the following
example, VLAN 1 is inactive because it does not contain any interfaces. The other VLANs contain enabled interfaces and are
active.
NOTE:
In a VLAN, the shutdown command stops Layer 3 (routed) traffic only. Layer 2 traffic continues to pass through
the VLAN. If the VLAN is not a routed VLAN (that is, configured with an IP address), the shutdown command has no
affect on VLAN traffic.
When you delete a VLAN (using the no interface vlan vlan-id command), any interfaces assigned to that VLAN are
assigned to the Default VLAN as untagged interfaces.
To create a port-based VLAN, use the following command.
● Configure a port-based VLAN (if the VLAN-ID is different from the Default VLAN ID) and enter INTERFACE VLAN mode.
CONFIGURATION mode
interface vlan vlan-id
To activate the VLAN, after you create a VLAN, assign interfaces in Layer 2 mode to the VLAN.
998
Virtual LANs (VLANs)