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ES-2724 User’s Guide
Chapter 8 VLAN
81
C
H A P T E R
8
VLAN
The type of screen you see here depends on the
VLAN Type
you selected in the
Switch Setup
screen. This chapter shows you how to configure 802.1Q tagged and port-based VLANs.
8.1 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).
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.
8.1.1 Forwarding Tagged and Untagged Frames
Each port on the switch is capable of passing tagged or untagged frames. To forward a frame
from an 802.1Q VLAN-aware switch to an 802.1Q VLAN-unaware switch, the switch first
decides where to forward the frame and then strips off the VLAN tag. To forward a frame
from an 802.1Q VLAN-unaware switch to an 802.1Q VLAN-aware switch, the switch first
decides where to forward the frame, and then inserts a VLAN tag reflecting the ingress port's
default VID. The default PVID is VLAN 1 for all ports, but this can be changed.
A broadcast frame (or a multicast frame for a multicast group that is known by the system) is
duplicated only on ports that are members of the VID (except the ingress port itself), thus
confining the broadcast to a specific domain.
TPID
2 Bytes
User Priority
3 Bits
CFI
1 Bit
VLAN ID
12 bits
Summary of Contents for ZyXEL Dimension ES-2724
Page 1: ...ES 2724 Intelligent Layer 3 Switch User s Guide Version 3 70 9 2006...
Page 2: ......
Page 7: ...ES 2724 User s Guide Safety Warnings 5 This product is recyclable Dispose of it properly...
Page 22: ...ES 2724 User s Guide 20 Table of Contents...
Page 30: ...ES 2724 User s Guide 28 List of Tables...
Page 36: ...ES 2724 User s Guide 34 Chapter 1 Getting to Know Your Switch...
Page 40: ...ES 2724 User s Guide 38 Chapter 2 Hardware Installation and Connection...
Page 48: ...ES 2724 User s Guide 46 Chapter 3 Hardware Overview...
Page 58: ...ES 2724 User s Guide 56 Chapter 4 The Web Configurator...
Page 64: ...ES 2724 User s Guide 62 Chapter 5 Initial Setup Example...
Page 70: ...ES 2724 User s Guide 68 Chapter 6 System Status and Port Statistics...
Page 82: ...ES 2724 User s Guide 80 Chapter 7 Basic Setting...
Page 95: ...ES 2724 User s Guide Chapter 8 VLAN 93 Figure 39 Port Based VLAN Setup All Connected...
Page 96: ...ES 2724 User s Guide 94 Chapter 8 VLAN Figure 40 Port Based VLAN Setup Port Isolation...
Page 98: ...ES 2724 User s Guide 96 Chapter 8 VLAN...
Page 107: ...ES 2724 User s Guide Chapter 11 Spanning Tree Protocol 105 Figure 45 RSTP Configuration...
Page 114: ...ES 2724 User s Guide 112 Chapter 11 Spanning Tree Protocol...
Page 126: ...ES 2724 User s Guide 124 Chapter 15 Link Aggregation...
Page 132: ...ES 2724 User s Guide 130 Chapter 16 Port Authentication...
Page 136: ...ES 2724 User s Guide 134 Chapter 17 Port Security...
Page 142: ...ES 2724 User s Guide 140 Chapter 18 Classifier Figure 61 Classifier Example...
Page 148: ...ES 2724 User s Guide 146 Chapter 19 Policy Rule Figure 64 Policy Example...
Page 151: ...ES 2724 User s Guide Chapter 20 Queuing Method 149 Figure 65 Queuing Method...
Page 158: ...ES 2724 User s Guide 156 Chapter 21 VLAN Stacking...
Page 189: ...ES 2724 User s Guide Chapter 28 DHCP 187 Figure 93 DHCP Relay Configuration Example...
Page 190: ...ES 2724 User s Guide 188 Chapter 28 DHCP...
Page 210: ...ES 2724 User s Guide 208 Chapter 30 Access Control...
Page 212: ...ES 2724 User s Guide 210 Chapter 31 Diagnostic...
Page 216: ...ES 2724 User s Guide 214 Chapter 32 Syslog...
Page 224: ...ES 2724 User s Guide 222 Chapter 33 Cluster Management...
Page 232: ...ES 2724 User s Guide 230 Chapter 37 Routing Table...
Page 268: ...ES 2724 User s Guide 266 Chapter 39 Introducing Commands...
Page 276: ...ES 2724 User s Guide 274 Chapter 40 User and Enable Mode Commands...
Page 290: ...ES 2724 User s Guide 288 Chapter 41 Configuration Mode Commands...
Page 306: ...ES 2724 User s Guide 304 Chapter 43 IEEE 802 1Q Tagged VLAN Commands...
Page 310: ...ES 2724 User s Guide 308 Chapter 45 Routing Domain Command Examples...
Page 320: ...ES 2724 User s Guide 318 Chapter 46 Troubleshooting...
Page 326: ...ES 2724 User s Guide 324 Appendix A Product Specifications...