AT-S63 Management Software Features Guide
Section VI: Virtual LANs
279
Tagged VLAN Overview
The second type of VLAN supported by the AT-S63 Management
Software is the
tagged VLAN
. VLAN membership in a tagged VLAN is
determined by information within the frames that are received on a port.
This differs from a port-based VLAN, where the PVIDs assigned to the
ports determine VLAN membership.
The VLAN information within an Ethernet frame is referred to as a
tag
or
tagged header
. A tag, which follows the source and destination addresses
in a frame, contains the VID of the VLAN to which the frame belongs (IEEE
802.3ac standard). As explained earlier in this chapter in “VLAN Identifier”
on page 273, this number uniquely identifies each VLAN in a network.
When a switch receives a frame with a VLAN tag, referred to as a
tagged
frame
, the switch forwards the frame only to those ports that share the
same VID.
A port to receive or transmit tagged frames is referred to as a
tagged port
.
Any network device connected to a tagged port must be IEEE 802.1Q-
compliant. This is the standard that outlines the requirements and
standards for tagging. The device must be able to process the tagged
information on received frames and add tagged information to transmitted
frames.
The benefit of a tagged VLAN is that the tagged ports can belong to more
than one VLAN at one time. This can greatly simplify the task of adding
shared devices to the network. For example, a server can be configured to
accept and return packets from many different VLANs simultaneously.
Tagged VLANs are also useful where multiple VLANs span across
switches. You can use one port per switch to connect all VLANs on the
switch to another switch.
The IEEE 802.1Q standard describes how this tagging information is used
to forward the traffic throughout the switch. The handling of frames tagged
with VIDs coming into a port is straightforward. If the incoming frame’s VID
tag matches one of the VIDs of a VLAN of which the port is a tagged
member, the frame is accepted and forwarded to the appropriate ports. If
the frame’s VID does not match any of the VLANs that the port is a
member of, the frame is discarded.
The parts of a tagged VLAN are much the same as those for a port-based
VLAN. They are:
VLAN Name
VLAN Identifier
Tagged and Untagged Ports
Summary of Contents for AT-S63
Page 14: ...Figures 14 ...
Page 18: ...Tables 18 ...
Page 28: ...28 Section I Basic Operations ...
Page 58: ...Chapter 1 Overview 58 ...
Page 76: ...Chapter 2 AT 9400Ts Stacks 76 Section I Basic Operations ...
Page 96: ...Chapter 5 MAC Address Table 96 Section I Basic Operations ...
Page 114: ...Chapter 8 Port Mirror 114 Section I Basic Operations ...
Page 116: ...116 Section II Advanced Operations ...
Page 146: ...Chapter 12 Access Control Lists 146 Section II Advanced Operations ...
Page 176: ...Chapter 14 Quality of Service 176 Section II Advanced Operations ...
Page 196: ...196 Section III Snooping Protocols ...
Page 204: ...Chapter 18 Multicast Listener Discovery Snooping 204 Section III Snooping Protocols ...
Page 216: ...Chapter 20 Ethernet Protection Switching Ring Snooping 216 Section III Snooping Protocols ...
Page 218: ...218 Section IV SNMPv3 ...
Page 234: ...234 Section V Spanning Tree Protocols ...
Page 268: ...268 Section VI Virtual LANs ...
Page 306: ...Chapter 27 Protected Ports VLANs 306 Section VI Virtual LANs ...
Page 320: ...320 Section VII Internet Protocol Routing ...
Page 360: ...Chapter 30 BOOTP Relay Agent 360 Section VII Routing ...
Page 370: ...Chapter 31 Virtual Router Redundancy Protocol 370 Section VII Routing ...
Page 372: ...372 Section VIII Port Security ...
Page 402: ...Chapter 33 802 1x Port based Network Access Control 402 Section VIII Port Security ...
Page 404: ...404 Section IX Management Security ...
Page 436: ...Chapter 36 PKI Certificates and SSL 436 Section IX Management Security ...
Page 454: ...Chapter 38 TACACS and RADIUS Protocols 454 Section IX Management Security ...
Page 462: ...Chapter 39 Management Access Control List 462 Section IX Management Security ...
Page 532: ...Appendix D MIB Objects 532 ...