ZyXEL Communications ALC1024, User Manual

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Commands with EEC
IEEE 802.1Q Tagged VLAN Commands 8-1
Chapter 8
IEEE 802.1Q Tagged VLAN Commands
This chapter describes the IEEE 802.1Q Tagged VLAN and associated commands.
8.1 IEEE 802.1Q Tagged VLAN Overview
The IEEE 802.1Q Tagged VLAN allows your line card to deliver tagged/untagged frames to and from its ports.
The standard gives the line card the ability to recognize VLAN-aware and VLAN-unaware devices and
automatically strips tagged frames destined for ports that would normally drop tagged frames.
8.2 IEEE 802.1Q Tagged VLAN -Tags
When a LAN bridge receives a frame from a workstation, the VLAN from whence it came must be known so the
bridge may respond, if necessary, to the source of the frame. This is accomplished by tagging. There are two kinds
of tagging:
1. Explicit Tagging
•
A VLAN identifier is added to the frame header that identifies the source VLAN.
2. Implicit Tagging
•
The MAC (Media Access Control) number, the port or other information is used to identify the source of a
VLAN frame.
The IEEE 802.1Q Tagged VLAN uses both explicit and implicit tagging.
8.3 VLAN-Aware/VLAN-Unaware Devices
It is important for the LAN bridge to determine what devices are VLAN-aware and VLAN-unaware so that it can
decide whether to forward a tagged frame (to a VLAN-aware device) or first strip the tag from a frame and then
forward it (to a VLAN-unaware device).
8.4 Filtering Databases
A filtering database stores and organizes VLAN registration information useful for switching frames to and from a
LAN bridge. A filtering database consists of a static entries (Static VLAN or SVLAN table) and dynamic entries
(Dynamic VLAN or DVLAN table).
8.4.1 Static Entries (SVLAN Table)
Static entry registration information is added, modified and removed by administrators only.