Cabletron Systems 802.1Q manual Chapter Virtual Local Area Networks, Defining VLANs

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CHAPTER 1

VIRTUAL LOCAL AREA NETWORKS

This chapter introduces the concepts of Virtual Local Area Networks (VLANs) and discusses the central concepts of IEEE 802.1Q VLANs. This chapter also contains information on how to contact Cabletron Systems for additional support related to VLANs.

1.1DEFINING VLANs

A Virtual Local Area Network is a group of devices that function as a single Local Area Network segment (broadcast domain). The devices that make up a particular VLAN may be widely separated, both by geography and location in the network.

The creation of VLANs allows users located in separate areas or connected to separate ports to belong to a single VLAN group. Users that are assigned to such a group will send and receive broadcast and multicast traffic as though they were all connected to a common network. VLAN aware switches isolate broadcast, multicast, and unknown traffic received from VLAN groups, so that traffic from stations in a VLAN are confined to that VLAN.

When stations are assigned to a VLAN, the performance of their network connection is not changed. Stations connected to switched ports do not sacrifice the performance of the dedicated switched link to participate in the VLAN. As a VLAN is not a physical location, but a membership, the network switches determine VLAN membership by associating a VLAN with a particular port or frame type.

Figure 1-1shows a simple example of a port based VLAN. Two buildings house the Sales and Finance departments of a single company, and each building has its own internal network. The stations in each building connect to a SmartSwitch in the basement. The two SmartSwitches are connected to one another with a high speed link.

802.1Q VLAN User’s Guide

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Contents 802.1Q Vlan User’s Guide Page 802.1Q Vlan User’s Guide 802.1Q Vlan User’s Guide Contents Contents Contents Contents 802.1Q Vlan User’s Guide Figures Tables Structure of this Guide Using this GuideDocument Conventions Related DocumentsDefining VLANs Chapter Virtual Local Area NetworksBuilding One Building Two 1 802.1Q VLANs Types of VLANsSecureFast VLANs Other Vlan StrategiesVlan Terms Benefits and RestrictionsData frame that does not have a Tag Header 1D Trunk Your email address Getting Help802.1Q Vlan User’s Guide Vlan Components Description1 Defining a Vlan Configuration ProcessClassifying Frames to a Vlan Customizing the Vlan Forwarding List Vlan Switch OperationReceiving Frames from Vlan Ports Inside the SwitchBroadcasts, Multicasts, and Unknown Unicasts Forwarding DecisionsKnown Unicasts Garp Switch Operation Switch Without VLANs Managing the SwitchSwitch Management with VLANs Switch with VLANsManaging the Switch Preparing for Vlan Configuration Summary of Vlan Local ManagementWhen to Use 802.1Q Vlan Configuration Menu ScreenHow to Access Menu Definitions Device Vlan Configuration Screen Device Vlan Configuration ScreenField Definitions 1 Defining a Vlan Renaming a Vlan Changing the Vlan to FID AssociationEnabling VLANs Deleting a VlanDisabling VLANs Paging Through the Vlan List Changing the Forwarding ModePort Assignment Configuration Screen Port Assignment Configuration ScreenPort Mode Changing the Port ModeAssigning a Vlan ID Paging Through the Port List Port Filtering Configuration ScreenPort Filtering Configuration Screen Vlan Lists Displaying Vlan IDs Associated with a PortSelecting the Type of Filtering for a Port Vlan Forwarding Configuration Screen Vlan Forwarding Configuration ScreenFrame Format Viewing Current Vlan PortsAdding Forwarding List Entries Paging Through Vlan Forwarding List EntriesDeleting Forwarding List Entries Changing the Frame Format Protocol Vlan Configuration ScreenProtocol Vlan Configuration Screen Selectable Feature Status Ether type Assigning a Protocol Family to a Vlan IDProtocol Vlan Configuration Screen Displaying the Protocol Types on Current Ports 10 Protocol Ports Configuration Screen Protocol Ports Configuration ScreenDelete ALL Quick Vlan Walkthrough Adding/Deleting Ports Associated with a Vlan ID802.1Q Vlan User’s Guide Hybrid 12 Walkthrough Stage Two 13 Walkthrough Stage Three 14 Walkthrough Stage Four Quick Vlan Walkthrough 15 Final Walkthrough Stage Chapter Examples Example 1, Single Switch OperationSwitch Configured for VLANs Solving the ProblemFrame Handling Example 2, Vlans Across Multiple Switches Example 2, VLANs Across Multiple Switches Switch Example 2, VLANs Across Multiple Switches Bridge 1 Broadcasts Frames Transmitting to Switch Transmitting to Bridge Example 3, 1D Trunk Connection to 802.1Q Vlan NetworkExample 3, 1D Trunk Connection to 802.1Q Vlan Network Solving the Problem Frame Handling 226318 Switch 2 Forwards to 1Q Trunk Examples Example 4, Isolating Network Traffic According to Protocol 11 Example 4, Isolating Traffic According to Protocol Switch Examples Example 4, Isolating Network Traffic According to Protocol Examples 802.1Q Vlan User’s Guide Numerics IndexIndex-2 802.1Q Vlan User’s Guide 802.1Q Vlan User’s Guide Index-3 Index Index-4 802.1Q Vlan User’s Guide
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