GS-2724 User’s Guide
85
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
Содержание GS-2724
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Страница 7: ...Safety Warnings GS 2724 User s Guide 7 ...
Страница 8: ...Safety Warnings GS 2724 User s Guide 8 ...
Страница 22: ...Table of Contents GS 2724 User s Guide 22 ...
Страница 30: ...List of Tables GS 2724 User s Guide 30 ...
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Страница 36: ...Chapter 1 Getting to Know Your Switch GS 2724 User s Guide 36 ...
Страница 40: ...Chapter 2 Hardware Installation and Connection GS 2724 User s Guide 40 ...
Страница 46: ...Chapter 3 Hardware Overview GS 2724 User s Guide 46 ...
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Страница 58: ...Chapter 4 The Web Configurator GS 2724 User s Guide 58 ...
Страница 64: ...Chapter 5 Initial Setup Example GS 2724 User s Guide 64 ...
Страница 70: ...Chapter 6 System Status and Port Statistics GS 2724 User s Guide 70 ...
Страница 84: ...84 ...
Страница 94: ...Chapter 8 VLAN GS 2724 User s Guide 94 Figure 36 Port Based VLAN Setup All connected ...
Страница 126: ...Chapter 16 Port Authentication GS 2724 User s Guide 126 ...
Страница 130: ...Chapter 17 Port Security GS 2724 User s Guide 130 ...
Страница 136: ...Chapter 18 Classifier GS 2724 User s Guide 136 Figure 58 Classifier Example ...
Страница 139: ...Chapter 19 Policy Rule GS 2724 User s Guide 139 Figure 59 Policy ...
Страница 145: ...Chapter 20 Queuing Method GS 2724 User s Guide 145 ...
Страница 146: ...Chapter 20 Queuing Method GS 2724 User s Guide 146 ...
Страница 152: ...Chapter 21 VLAN Stacking GS 2724 User s Guide 152 ...
Страница 165: ...165 PART IV IP Application Static Route 167 RIP 169 IGMP 171 Differentiated Services 173 DHCP 177 ...
Страница 166: ...166 ...
Страница 183: ...Chapter 27 DHCP GS 2724 User s Guide 183 Figure 89 DHCP Relay Configuration Example ...
Страница 184: ...Chapter 27 DHCP GS 2724 User s Guide 184 ...
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Страница 210: ...Chapter 31 Syslog GS 2724 User s Guide 210 ...
Страница 224: ...Chapter 36 Routing Table GS 2724 User s Guide 224 ...
Страница 228: ...228 ...
Страница 262: ...Chapter 38 Introducing Commands GS 2724 User s Guide 262 ...
Страница 296: ...Chapter 42 IEEE 802 1Q Tagged VLAN Commands GS 2724 User s Guide 296 ...
Страница 300: ...Chapter 44 Routing Domain Command Examples GS 2724 User s Guide 300 ...
Страница 304: ...304 ...
Страница 312: ...Appendix B Changing a Fuse GS 2724 User s Guide 312 ...
Страница 332: ...Appendix E Common Services GS 2724 User s Guide 332 ...
Страница 336: ...Appendix F Legal Information GS 2724 User s Guide 336 ...
Страница 348: ...Index GS 2724 User s Guide 348 ...