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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 (2^12) VLANs. Note that user priority and
VLAN ID are independent of each other. A frame with VID (VLAN Identifier) of null (0) is
2.
GVRP (GARP VLAN Registration Protocol) defines a way for switches to automatically configure switches in a
VLAN network.
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Страница 8: ...Safety Warnings IES 1248 71 73 User s Guide 8 ...
Страница 38: ...List of Tables IES 1248 71 73 User s Guide 38 ...
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Страница 51: ...Chapter 2 Hardware Installation IES 1248 71 73 User s Guide 51 Figure 6 IES 1248 Frame Ground Frame Ground ...
Страница 52: ...Chapter 2 Hardware Installation IES 1248 71 73 User s Guide 52 ...
Страница 60: ...Chapter 3 Front Panel Connections IES 1248 71 73 User s Guide 60 ...
Страница 68: ...Chapter 4 MDF Connections IES 1248 71 73 User s Guide 68 ...
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Страница 81: ...Chapter 7 Introducing the Web Configurator IES 1248 71 73 User s Guide 81 Figure 30 Logout ...
Страница 82: ...Chapter 7 Introducing the Web Configurator IES 1248 71 73 User s Guide 82 ...
Страница 110: ...Chapter 12 User Account IES 1248 71 73 User s Guide 110 ...
Страница 116: ...Chapter 13 Switch Setup IES 1248 71 73 User s Guide 116 ...
Страница 118: ...Chapter 14 IP Setup IES 1248 71 73 User s Guide 118 ...
Страница 150: ...Chapter 17 xDSL Profiles Setup IES 1248 71 73 User s Guide 150 ...
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Страница 166: ...Chapter 19 VLAN IES 1248 71 73 User s Guide 166 ...
Страница 184: ...Chapter 22 Multicast VLAN IES 1248 71 73 User s Guide 184 ...
Страница 216: ...Chapter 30 2684 Routed Mode IES 1248 71 73 User s Guide 216 ...
Страница 222: ...Chapter 31 PPPoA to PPPoE IES 1248 71 73 User s Guide 222 ...
Страница 226: ...Chapter 32 DSCP IES 1248 71 73 User s Guide 226 ...
Страница 240: ...Chapter 36 Syslog IES 1248 71 73 User s Guide 240 ...
Страница 248: ...Chapter 37 Access Control IES 1248 71 73 User s Guide 248 ...
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Страница 259: ...Chapter 39 Alarm IES 1248 71 73 User s Guide 259 ...
Страница 260: ...Chapter 39 Alarm IES 1248 71 73 User s Guide 260 ...
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Страница 296: ...Chapter 44 Commands IES 1248 71 73 User s Guide 296 ...
Страница 304: ...Chapter 45 Command Examples IES 1248 71 73 User s Guide 304 ...
Страница 320: ...Chapter 47 DHCP Commands IES 1248 71 73 User s Guide 320 ...
Страница 328: ...Chapter 48 IEEE 802 1Q Tagged VLAN Commands IES 1248 71 73 User s Guide 328 ...
Страница 334: ...Chapter 49 MAC Commands IES 1248 71 73 User s Guide 334 ...
Страница 348: ...Chapter 50 IGMP Commands IES 1248 71 73 User s Guide 348 ...
Страница 352: ...Chapter 51 Packet Filter Commands IES 1248 71 73 User s Guide 352 ...
Страница 362: ...Chapter 53 Firmware and Configuration File Maintenance IES 1248 71 73 User s Guide 362 ...
Страница 394: ...Chapter 55 ADSL Commands IES 1248 71 73 User s Guide 394 ...
Страница 418: ...Chapter 56 Virtual Channel Management IES 1248 71 73 User s Guide 418 ...
Страница 424: ...Chapter 57 ACL Commands IES 1248 71 73 User s Guide 424 ...
Страница 436: ...Chapter 58 Troubleshooting IES 1248 71 73 User s Guide 436 ...
Страница 437: ...437 PART VI Appendices and Index Product Specifications 439 Legal Information 449 Index 457 ...
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Страница 448: ...Appendix B Removing and Installing a Fuse IES 1248 71 73 User s Guide 448 ...
Страница 452: ...Appendix C Legal Information IES 1248 71 73 User s Guide 452 ...
Страница 464: ...Index IES 1248 71 73 User s Guide 464 ...