GS-2750 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 for the TPID (Tag Protocol Identifier, residing within
the type/length field of the Ethernet frame) and two bytes for the TCI (Tag Control
Information, starting 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 the value 4095 (FFF) is reserved, so the maximum possible
number of VLAN configurations is 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-2750
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Страница 7: ...Safety Warnings GS 2750 User s Guide 7 This product is recyclable Dispose of it properly ...
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Страница 40: ...Chapter 2 Hardware Installation and Connection GS 2750 User s Guide 40 ...
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Страница 58: ...Chapter 4 The Web Configurator GS 2750 User s Guide 58 ...
Страница 64: ...Chapter 5 Initial Setup Example GS 2750 User s Guide 64 ...
Страница 70: ...Chapter 6 System Status and Port Statistics GS 2750 User s Guide 70 ...
Страница 82: ...Chapter 7 Basic Setting GS 2750 User s Guide 82 ...
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Страница 115: ...Chapter 11 Spanning Tree Protocol GS 2750 User s Guide 115 Figure 52 Advanced Application Spanning Tree Protocol MSTP ...
Страница 120: ...Chapter 11 Spanning Tree Protocol GS 2750 User s Guide 120 ...
Страница 134: ...Chapter 15 Link Aggregation GS 2750 User s Guide 134 ...
Страница 144: ...Chapter 17 Port Security GS 2750 User s Guide 144 ...
Страница 155: ...Chapter 19 Policy Rule GS 2750 User s Guide 155 Figure 73 Policy Example example ...
Страница 156: ...Chapter 19 Policy Rule GS 2750 User s Guide 156 ...
Страница 160: ...Chapter 20 Queuing Method GS 2750 User s Guide 160 ...
Страница 166: ...Chapter 21 VLAN Stacking GS 2750 User s Guide 166 ...
Страница 194: ...Chapter 23 Authentication Accounting GS 2750 User s Guide 194 ...
Страница 219: ...219 PART IV IP Application Static Routing 221 RIP 223 Differentiated Services 225 DHCP 233 VRRP 243 ...
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Страница 232: ...Chapter 28 Differentiated Services GS 2750 User s Guide 232 ...
Страница 242: ...Chapter 29 DHCP GS 2750 User s Guide 242 ...
Страница 252: ...Chapter 30 VRRP GS 2750 User s Guide 252 ...
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Страница 278: ...Chapter 32 Access Control GS 2750 User s Guide 278 ...
Страница 280: ...Chapter 33 Diagnostic GS 2750 User s Guide 280 ...
Страница 284: ...Chapter 34 Syslog GS 2750 User s Guide 284 ...
Страница 298: ...Chapter 39 Routing Table GS 2750 User s Guide 298 ...
Страница 301: ...301 PART VI Product Specifications Product Specifications 303 ...
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Страница 309: ...309 PART VII Appendices and Index IP Addresses and Subnetting 311 Legal Information 319 Customer Support 323 Index 329 ...
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Страница 322: ...Appendix B Legal Information GS 2750 User s Guide 322 ...
Страница 328: ...Appendix C Customer Support GS 2750 User s Guide 328 ...