ZyXEL MI-7248 User Guide - Page 83

Introduction to VLANs, Introduction to IEEE 802.1Q Tagged VLANs

Page 83 highlights

CHAPTER 13 VLAN 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. " 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 field of the Ethernet frame) and two bytes of TCI (Tag Control Information, starts after the source address field of the Ethernet frame). MS-7206 User's Guide 83

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MS-7206 User’s Guide
83
C
HAPTER
13
VLAN
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.
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 field of the Ethernet frame) and two bytes of TCI (Tag Control Information, starts
after the source address field of the Ethernet frame).