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IES-1248-51 User’s Guide
Chapter 19 VLAN
147
C
H A P T E R
19
VLAN
This chapter shows you how to configure IEEE 802.1Q tagged VLANs.
19.1 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 that a VLAN is unidirectional, it only governs outgoing traffic.
19.2 Introduction to IEEE 802.1Q Tagged VLAN
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 device on which they were
created. The VLANs can be created statically by hand or configured dynamically using
GVRP.
2
The VLAN ID associates a frame with a specific VLAN and provides the information
that devices 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).
The CFI (Canonical Format Indicator) is a single-bit flag, always set to zero for Ethernet
switches. If a frame received at an Ethernet port has a CFI set to 1, then that frame should not
be forwarded as it is to an untagged port. The remaining twelve bits define the VLAN ID,
giving a possible maximum number of 4,096 (212) VLANs. Note that user priority and VLAN
2.
GVRP (GARP VLAN Registration Protocol) defines a way for switches to automatically configure
switches in a VLAN network.
Содержание IES-1248-51
Страница 1: ...IES 1248 51 ADSL2 IP DSLAM User s Guide Version 3 51 ABQ 1 3 2006 ...
Страница 4: ...IES 1248 51 User s Guide 4 Interference Statements and Warnings ...
Страница 22: ...IES 1248 51 User s Guide 22 Table of Contents Index 379 ...
Страница 30: ...IES 1248 51 User s Guide 30 List of Figures ...
Страница 34: ...IES 1248 51 User s Guide 34 List of Tables ...
Страница 47: ...IES 1248 51 User s Guide Chapter 2 Hardware Installation 47 Figure 6 IES 1248 51 Frame Ground Frame Ground ...
Страница 48: ...IES 1248 51 User s Guide 48 Chapter 2 Hardware Installation ...
Страница 62: ...IES 1248 51 User s Guide 62 Chapter 4 MDF Connections ...
Страница 73: ...IES 1248 51 User s Guide Chapter 7 Introducing the Web Configurator 73 Figure 29 Logout ...
Страница 74: ...IES 1248 51 User s Guide 74 Chapter 7 Introducing the Web Configurator ...
Страница 88: ...IES 1248 51 User s Guide 88 Chapter 9 Home and Port Statistics Screens ...
Страница 90: ...IES 1248 51 User s Guide 90 Chapter 10 System Information Figure 44 System Info ...
Страница 98: ...IES 1248 51 User s Guide 98 Chapter 12 User Account ...
Страница 104: ...IES 1248 51 User s Guide 104 Chapter 13 Switch Setup ...
Страница 106: ...IES 1248 51 User s Guide 106 Chapter 14 IP Setup ...
Страница 126: ...IES 1248 51 User s Guide 126 Chapter 16 xDSL Port Setup ...
Страница 140: ...IES 1248 51 User s Guide 140 Chapter 17 xDSL Profiles Setup ...
Страница 154: ...IES 1248 51 User s Guide 154 Chapter 19 VLAN ...
Страница 188: ...IES 1248 51 User s Guide 188 Chapter 28 2684 Routed Mode ...
Страница 192: ...IES 1248 51 User s Guide 192 Chapter 30 Syslog ...
Страница 210: ...IES 1248 51 User s Guide 210 Chapter 33 Alarm ...
Страница 240: ...IES 1248 51 User s Guide 240 Chapter 38 Commands ...
Страница 256: ...IES 1248 51 User s Guide 256 Chapter 40 Alarm Commands ...
Страница 262: ...IES 1248 51 User s Guide 262 Chapter 41 DHCP Relay Commands ...
Страница 282: ...IES 1248 51 User s Guide 282 Chapter 44 IGMP Commands ...
Страница 286: ...IES 1248 51 User s Guide 286 Chapter 45 Packet Filter Commands ...
Страница 292: ...IES 1248 51 User s Guide 292 Chapter 46 IP Commands ...
Страница 302: ...IES 1248 51 User s Guide 302 Chapter 48 SNMP ...
Страница 338: ...IES 1248 51 User s Guide 338 Chapter 49 ADSL Commands ...
Страница 358: ...IES 1248 51 User s Guide 358 Chapter 50 Virtual Channel Management ...
Страница 370: ...IES 1248 51 User s Guide 370 Chapter 51 Troubleshooting ...
Страница 378: ...IES 1248 51 User s Guide 378 ...