Vlan; Chapter 13 Vlan; Introduction To Vlans; Introduction To Ieee 802.1Q Tagged Vlans - ZyXEL Communications MS-7206 - EDITION 1 Manual

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H A P T E R
This chapter introduces VLANs and then describes the screens you use to
configure VLAN settings.

13.1 Introduction to VLANs

A VLAN (Virtual Local Area Network) allows a physical network to be partitioned
into multiple logical networks. Devices on a logical network belong to one group. A
device can belong to more than one group. With VLAN, a device cannot directly
talk to or hear from devices that are not in the same group(s); the traffic must
first go through a router.
In MTU (Multi-Tenant Unit) applications, VLAN is vital in providing isolation and
security among the subscribers. When properly configured, VLAN prevents one
subscriber from accessing the network resources of another on the same LAN,
thus a user will not see the printers and hard disks of another user in the same
building.
VLAN also increases network performance by limiting broadcasts to a smaller and
more manageable logical broadcast domain. In traditional switched environments,
all broadcast packets go to each and every individual port. With VLAN, all
broadcasts are confined to a specific broadcast domain.
Note: VLAN is unidirectional; it only governs outgoing traffic.

13.2 Introduction to IEEE 802.1Q Tagged VLANs

A tagged VLAN uses an explicit tag (VLAN ID) in the MAC header to identify the
VLAN membership of a frame across bridges - they are not confined to the switch
on which they were created. The VLANs can be created statically by hand or
dynamically through GVRP. The VLAN ID associates a frame with a specific VLAN
and provides the information that switches need to process the frame across the
network. A tagged frame is four bytes longer than an untagged frame and
contains two bytes of TPID (Tag Protocol Identifier, residing within the type/length
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VLAN

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