System information

VLAN Management
VLANs
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If a frame is VLAN-tagged, a four-byte VLAN tag is added to each Ethernet frame,
increasing the maximum frame size from 1518 to 1522. The tag contains a VLAN
ID between 1 and 4094, and a VLAN Priority Tag (VPT) between 0 and 7. See QoS
Features and Components 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.
The frame is discarded at the ingress port if Ingress Filtering is enabled and the
ingress port is not a member of the VLAN to which the packet belongs. A frame is
regarded as priority-tagged only if the VID in its VLAN tag is 0.
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.
The egress port:
• 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, including:
• Voice VLAN: For more information refer to the Voice VLAN section.
• Default VLAN: For more information refer to the Configuring Default VLAN
Settings section.
• Management VLAN: For more information refer to the IP Addressing
section.