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Cabletron Systems 802.1Q manual Receiving Frames from VLAN Ports, Untagged Frames

Models: 802.1Q

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2.4.1Receiving Frames from VLAN Ports

Chapter 2: VLAN Operation

Figure 2-1depicts the inside of a switch with six ports, numbered one through six. The switch has been conﬁgured to associate VLAN A and B with FID 2, VLAN C and D with FID 3, and VLAN E with FID 4. Port 6 has been classiﬁed as a 1Q Trunk Port. This classiﬁcation establishes that all VLANs are members of the Port VLAN List for Port 6 and the frames transmitted for all VLANs will contain a tag header. Also the PVID for Port 6 is set to the default VLAN with its corresponding relationship to FID 1. Although untagged frames are not usually present on a 1Q Trunk Port, any untagged frames received would need to be classiﬁed if the port has not been conﬁgured to drop all untagged frames.

Port 1 Port 2Port 3

A	B	C
FID 2	FID 2	FID 3
D	E	Default
FID 3	FID 4	FID 1
Port 4	Port 5	Port 6

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Figure 2-1 Inside the Switch

2.4.1Receiving Frames from VLAN Ports

When a switch is placed in 802.1Q Operational Mode, every frame received by the switch must belong, or be assigned, to a VLAN.

Untagged Frames

The switch receives a frame from Port 1 and examines the frame. The switch notices that this frame does not currently have a VLAN tag. The switch recognizes that Port 1 is a member of VLAN A and classiﬁes the frame as such. In this fashion, all untagged frames entering a VLAN switch assume membership in a VLAN.

NOTE

A VLAN ID is always assigned to a port. By default, it is the Default VLAN (VLAN ID = 1).

2-4	802.1Q VLAN User’s Guide

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Cabletron Systems 802.1Q manual Receiving Frames from VLAN Ports, Untagged Frames

Contents

802.1Q VLAN User’s Guide 9032599-02Page 802.1Q VLAN User’s Guide 802.1Q VLAN User’s Guide CONTENTS PREFACECHAPTER VIRTUAL LOCAL AREA NETWORKSContents VLAN CONFIGURATIONCHAPTER 802.1Q VLAN User’s GuideContents CHAPTEREXAMPLES 802.1Q VLAN User’s GuideContents 802.1Q VLAN User’s GuideFIGURES 802.1Q VLAN User’s GuideTABLES 802.1Q VLAN Configuration Menu Screen Menu Items802.1Q VLAN User’s Guide viiiUSING THIS GUIDE PREFACESTRUCTURE OF THIS GUIDE RELATED DOCUMENTS DOCUMENT CONVENTIONSCHAPTER VIRTUAL LOCAL AREA NETWORKS 1.1 DEFINING VLANsBuilding One Building Two1.2 TYPES OF VLANs 1.2.1 802.1Q VLANs1.2.2 SecureFast VLANs 1.2.3 Other VLAN Strategies1.3 BENEFITS AND RESTRICTIONS 1.4 VLAN TERMSA data frame that does not have a Tag Header 1D Trunk Generic Attribute Registration Protocol GARPGARP VLAN Registration Protocol GVRP GARP Multicast Registration Protocol GMRP1.5 GETTING HELP Chapter 1 Virtual Local Area Networks 802.1Q VLAN User’s GuideCHAPTER VLAN OPERATION 2.1 DESCRIPTION2.2 VLAN COMPONENTS 2.3 CONFIGURATION PROCESS 2.3.1 Deﬁning a VLAN2.3.2 Classifying Frames to a VLAN Chapter 2 VLAN Operation2.4 VLAN SWITCH OPERATION 2.3.3 Customizing the VLAN Forwarding List2.4.1 Receiving Frames from VLAN Ports Untagged Frames2.4.2 Forwarding Decisions 2.4.2.1 Broadcasts, Multicasts, and Unknown Unicasts2.4.2.2 Known Unicasts Tagged Frames2.5 GARP SWITCH OPERATION CHAPTER VLAN CONFIGURATION 3.1 MANAGING THE SWITCH3.1.1 Switch Without VLANs 802.1Q Switch3.1.2 Switch with VLANs 802.1Q Switch2. Use the Port Assignment Configuration screen for the following 3.2 SUMMARY OF VLAN LOCAL MANAGEMENT 3.2.1 Preparing for VLAN Conﬁguration3.3 802.1Q VLAN CONFIGURATION MENU SCREEN When to UseHow to Access Screen ExampleFigure 3-4 802.1Q VLAN Conﬁguration Menu Screen Menu Deﬁnitions 802.1Q VLAN Conﬁguration Menu Screen802.1Q VLAN User’s Guide Table 3-1 802.1Q VLAN Conﬁguration Menu Screen Menu Items3.4 DEVICE VLAN CONFIGURATION SCREEN When to UseHow to Access Screen ExampleField Deﬁnitions Device VLAN Conﬁguration Screen802.1Q VLAN User’s Guide Table 3-2 Device VLAN Conﬁguration Screen Field Deﬁnitions3.4.1 Deﬁning a VLAN 3.4.2 Changing the VLAN to FID Association 3.4.3 Renaming a VLAN3.4.4 Deleting a VLAN 3.4.5 Enabling VLANs3.4.6 Disabling VLANs The default VLAN cannot be deleted from the list3.4.7 Changing the Forwarding Mode 3.4.8 Paging Through the VLAN ListThe default VLAN cannot be disabled 3.5 PORT ASSIGNMENT CONFIGURATION SCREEN When to UseHow to Access Screen Example3.5.1 Changing the Port Mode Field Deﬁnitions3.5.2 Assigning a VLAN ID 3.6 PORT FILTERING CONFIGURATION SCREEN 3.5.3 Paging Through the Port ListWhen to Use How to Access Screen ExampleChapter 3 VLAN Conﬁguration 3-183.6.1 Displaying VLAN IDs Associated with a Port Field Deﬁnitions3.6.2 Selecting the Type of Filtering for a Port 3.7 VLAN FORWARDING CONFIGURATION SCREEN When to UseHow to Access Screen Example3.7.1 Viewing Current VLAN Ports Field DeﬁnitionsSee the frame format Tagged or Untagged for the frames 3.7.2 Paging Through VLAN Forwarding List Entries 3.7.3 Adding Forwarding List Entries3.7.4 Deleting Forwarding List Entries 3.8 PROTOCOL VLAN CONFIGURATION SCREEN 3.7.5 Changing the Frame FormatWhen to Use How to Access Screen ExampleProtocol VLAN Conﬁguration Screen 802.1Q VLAN User’s GuideField Deﬁnitions Chapter 3 VLAN Conﬁguration3-26 802.1Q VLAN User’s GuideProtocol VLAN Conﬁguration Screen 802.1Q VLAN User’s Guide3-27 Table 3-6 Protocol VLAN Conﬁguration Screen Field Deﬁnitions Cont’d3.8.1 Displaying the Current Protocol, VLAN ID, and Port Assignments 3.8.2 Assigning a Protocol Family to a VLAN IDProtocol VLAN Conﬁguration Screen To see if there are VLANs currently assigned to the ProtocolTIP displayed in the Protocol ﬁeld, press ENTER 802.1Q VLAN User’s Guide3.8.3 Displaying the Protocol Types on Current Ports 3.9 PROTOCOL PORTS CONFIGURATION SCREEN When to UseHow to Access Screen ExampleField Deﬁnitions Chapter 3 VLAN Conﬁguration3-32 802.1Q VLAN User’s Guide3.9.1 Adding/Deleting Ports Associated with a VLAN ID 3.10 QUICK VLAN WALKTHROUGH6. Use the arrow keys to highlight the ADD/DEL field It is now time to assign a port to this new VLAN Figure 3-12 Walkthrough Stage Two Figure 3-13 Walkthrough Stage Three 17. Press the SPACE bar to toggle the field to display Enabled 21. Use the arrow keys to highlight the Port field Chapter 3 VLAN Conﬁguration 3-40802.1Q VLAN User’s Guide Figure 3-15 Final Walkthrough Stage802.1Q Switch 4.1 EXAMPLE 1, SINGLE SWITCH OPERATIONCHAPTER EXAMPLES R1 R2 R34.1.1 Solving the Problem 802.1Q SwitchB3 B2 B1 4.1.2 Frame Handling 4.2 EXAMPLE 2, VLANS ACROSS MULTIPLE SWITCHES 4.2.1 Solving the Problem Figure 4-3 Example 2, VLANs Across Multiple SwitchesSwitch 4 is set as follows Switch 2 is set as follows 4.2.2 Frame Handling Figure 4-4 Bridge 1 Broadcasts FramesFigure 4-5 Transmitting to Switch 4.3 EXAMPLE 3, 1D TRUNK CONNECTION TO 802.1Q VLAN NETWORK Figure 4-6 Transmitting to BridgeFigure 4-7 Example 3, 1D Trunk Connection to 802.1Q VLAN Network User BGreen Incorporated 4.3.1 Solving the Problem 4.3.2 Frame Handling Figure 4-8 Bridge 1 Broadcasts Frames Figure 4-9 Switch 2 Forwards to 1Q Trunk Figure 4-10 Switch 1 Forwards to 1D TrunkSwitch 1 checks the Filtering Database for the MAC address of User B. User B’s MAC address is located, and Port 2 is identified as User B’s location. The frame is then checked for eligibility and frame format for Port 2. Since Port 2 is a 1Q Trunk port, it is eligible to transmit frames for all VLANs. The frame is tagged and transmitted out Port 4.4 EXAMPLE 4, ISOLATING NETWORK TRAFFIC ACCORDING TO PROTOCOL 4.4.1 Solving the Problem Figure 4-11 Example 4, Isolating Trafﬁc According to ProtocolSwitch 3 is set as follows Switch 5 is set as follows Port 2, VLAN ID 6, Protocol AppleTalk Chapter 4 Examples 4-22802.1Q VLAN User’s Guide INDEX NumericsIndex Index-2802.1Q VLAN User’s Guide Index 802.1Q VLAN User’s GuideIndex-3 Index Index-4802.1Q VLAN User’s Guide