Chapter 6 Broadband
VSG1432-B101 Series User’s Guide
90
In Multi-Tenant Unit (MTU) 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.
Introduction to IEEE 802.1Q Tagged VLAN
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).
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
VLANs. Note that user priority and VLAN ID are independent of each other. A
frame with VID (VLAN Identifier) of null (0) is called a priority frame, meaning that
only the priority level is significant and the default VID of the ingress port is given
as the VID of the frame. Of the 4096 possible VIDs, a VID of 0 is used to identify
priority frames and value 4095 (FFF) is reserved, so the maximum possible VLAN
configurations are 4,094.
TPID
2 Bytes
User Priority
3 Bits
CFI
1 Bit
VLAN ID
12 Bits
Summary of Contents for VSG1432-B101 - V1.10
Page 2: ......
Page 8: ...Safety Warnings VSG1432 B101 Series User s Guide 8 ...
Page 10: ...Contents Overview VSG1432 B101 Series User s Guide 10 ...
Page 20: ...Table of Contents VSG1432 B101 Series User s Guide 20 ...
Page 21: ...21 PART I User s Guide ...
Page 22: ...22 ...
Page 40: ...Chapter 2 The Web Configurator VSG1432 B101 Series User s Guide 40 ...
Page 67: ...67 PART II Technical Reference ...
Page 68: ...68 ...
Page 74: ...Chapter 5 Network Map and Status Screens VSG1432 B101 Series User s Guide 74 ...
Page 146: ...Chapter 8 Home Networking VSG1432 B101 Series User s Guide 146 ...
Page 150: ...Chapter 9 Static Routing VSG1432 B101 Series User s Guide 150 ...
Page 174: ...Chapter 11 Policy Forwarding VSG1432 B101 Series User s Guide 174 ...
Page 192: ...Chapter 12 Network Address Translation NAT VSG1432 B101 Series User s Guide 192 ...
Page 198: ...Chapter 13 Dynamic DNS Setup VSG1432 B101 Series User s Guide 198 ...
Page 224: ...Chapter 16 Firewall VSG1432 B101 Series User s Guide 224 ...
Page 230: ...Chapter 18 Parental Control VSG1432 B101 Series User s Guide 230 ...
Page 278: ...Chapter 25 Traffic Status VSG1432 B101 Series User s Guide 278 ...
Page 282: ...Chapter 26 IGMP Status VSG1432 B101 Series User s Guide 282 ...
Page 290: ...Chapter 28 Remote Management VSG1432 B101 Series User s Guide 290 ...
Page 294: ...Chapter 29 Time Settings VSG1432 B101 Series User s Guide 294 ...
Page 298: ...Chapter 30 Logs Setting VSG1432 B101 Series User s Guide 298 ...
Page 314: ...Chapter 34 Troubleshooting VSG1432 B101 Series User s Guide 314 ...
Page 344: ...Appendix A Setting up Your Computer s IP Address VSG1432 B101 Series User s Guide 344 ...
Page 354: ...Appendix B IP Addresses and Subnetting VSG1432 B101 Series User s Guide 354 ...
Page 380: ...Appendix D Wireless LANs VSG1432 B101 Series User s Guide 380 ...