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Chapter 6 VLAN Management
VLAN Management
This section covers the following topics:
•
Overview
•
VLANs
•
Interfaces
•
VLAN Memberships
•
Voice VLAN
Overview
A VLAN is a logical group of ports that enables devices associated with it to
communicate with each other over the Ethernet MAC layer, regardless of the
physical LAN segment of the bridged network to which they are connected .
Each VLAN is configured with a unique VID (VLAN ID) with a value from 1 to 4094 .
A port on a device in a bridged network is a member of a VLAN if it can send data
to and receive data from the VLAN . A port is an untagged member of a VLAN if all
packets destined for that port into the VLAN have no VLAN tag . A port is a tagged
member of a VLAN if all packets destined for that port into the VLAN have a VLAN
tag . A port can be a member of one untagged VLAN and can be a member of
several tagged VLANs .
A port in VLAN Access Mode can be part of only one VLAN . If it is in Trunk Mode,
the port can be part of one or more VLANs .
VLANs address security and scalability issues . Traffic from a VLAN stays within the
VLAN, and terminates at devices in the VLAN . It also eases network configuration
by logically connecting devices without physically relocating those devices .
If a frame is VLAN-tagged, a four-byte VLAN tag is added to each Ethernet frame .
The tag contains a VLAN ID between 1 and 4094, and a VLAN Priority Tag (VPT)
between 0 and 7 . See Quality of Service for details about VPT .
When a frame enters a VLAN-aware device, it is classified as belonging to a VLAN,
based on the four-byte VLAN tag in the frame .
If there is no VLAN tag in the frame or the frame is priority-tagged only, the frame
is classified to the VLAN based on the PVID (Port VLAN Identifier) configured at
the ingress port where the frame is received .
Frames belonging to a VLAN remain within the VLAN . This is achieved by sending
or forwarding a frame only to egress ports that are members of the target VLAN .
An egress port may be a tagged or untagged member of a VLAN . T he egress port
peforms the following actions:
Adds a VLAN tag to the frame if the egress port is a tagged member of the
•
target VLAN, and the original frame does not have a VLAN tag .
•
Removes the VLAN tag from the frame if the egress port is an untagged
member of the target VLAN, and the original frame has a VLAN tag .
VLAN Roles
All VLAN traffic (Unicast/Broadcast/Multicast) remains within its VLAN . Devices
attached to different VLANs do not have direct connectivity to each other over
the Ethernet MAC layer .
Device VLANs can only be created statically . Some VLANs can have additional
roles:
Voice VLAN—For more information refer to Voice VLAN .
•
•
Guest VLAN—For more information refer to Security: Network Access Control .
Default VLAN—For more information refer to VLANs .
•
•
Management VLAN—For more information refer to the IPv4 Interface page
VLAN Configuration Workflow
To configure VLANs, do the following:
If required, change the default VLAN by using the VLAN Management section .
1 .
Create the required VLANs by using the VLANs section .
2 .
Set the desired VLAN-related configuration for portsusing the Interfaces
3 .
section .
Chapter 6 VLAN Management
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