Asante Technologies 3500 Series user manual Switching Concepts, Port-Based VLANs

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Chapter 7. Switching Concepts

A bridge is a hardware device used to connect multiple networks into one big network. However, when a bridge receives a broadcast from one interface, it will forward the frame to all interfaces and flood the wire, easily overwhelming the network.

The traditional solution to the problem of broadcast flooding is to use a router. The disadvantages of a router include higher cost (the initial purchase price and higher maintenance costs) and slower rate pf processing incoming data, leading to increased latency with decreased network performance. A switch (basically a complex bridge) can process data at a faster rate than a router, and can limit unnecessary flooded traffic by learning the addresses of the stations on the system. A switch can be used to create broadcasts domains (via VLANs), and can be employed as an alternate solution to using routers to contain broadcast flooding.

While a bridge connects network segments via interfaces, a switch connects segments via its ports, like a hub. But, unlike a hub, the ports of a switch can be configured to belong to a specific network, thereby separating traffic, providing security and reducing overall network congestion.

The following sections provide brief explanations of some of the concepts related to switching. If more information is required, please refer to networking textbooks, online resources (i.e. www.oreillynet.com) or your MIS manager.

7.1 VLANs

A virtual local area network, or VLAN, is a logical grouping that allows stations to communicate as if they were physically connected to a single LAN, independent of the actual physical configuration of a network. A VLAN localizes flooded traffic to parts of LAN segments, rather than to an entire LAN, offering a simple solution to network performance, security and bandwidth utilization.

7.1.1 Port-Based VLANs

Port-based VLANs are the simplest of many VLAN approaches (others are based on MAC addresses, protocol type, and higher layers that are not currently supported by the IEEE 802.1Q standard) that solve the problem of unnecessary flooding. The switch currently supports port-based VLANs in compliance with the IEEE standard.

A port-based VLAN allows the administrator to assign individual ports to a VLAN. Any broadcast (sent to every user in the network) or multicast (sent to a pre-specified group of users) traffic received on a port in a VLAN are limited by the VLAN boundaries so that only workstations whose ports are members of the same VLAN see those frames.

7.1.2 VLAN ID and Tagged Frames

The IntraCore 3524 supports 64 manually configurable VLANs. Each VLAN is identified by a 12-bit (1-4095) VLAN ID (VID). No two VLANs may have the same VID if they reside on the same switch. However, by assigning the same VID to VLANs on multiple switches, the broadcast domain may be extended over a large network. The switch is shipped with a single default VLAN, with a VID of 0.

In a network with only one switch, the switch itself keeps track of which ports belong to which VLAN. In a network with multiple switches, the information about which VLAN an Ethernet frame belongs to must be sent along with the frame. This is done by inserting a tag field, as defined in IEEE 802.1Q, in the frame. The tag includes a VLAN ID field that matches the VID assigned to a VLAN on the switch. The switch will then assign the frame to the VLAN represented by the tag field.

A port map is used to specify which ports are members of each VLAN. Each VLAN has a set of untagged ports that specifies which port members of the VLAN transmit only untagged frames. The untagged set can be a subset of the port map, or it can be the same as the port map. If a port is in the VLAN port map and not in the VLAN untagged set, that port transmits tagged frames only. The switch includes all ports in its untagged set by default.

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Contents IntraCore 3500 Series Quick Start Guide IntraCore 3500 Series Gigabit Ethernet Switches User’s ManualTable of Contents Page Introduction Package Contents1 IC3524 Models LEDs4810/100 2 IC3548-2GT#49 Front and Back Panel DescriptionsManagement and Configuration Web-Based Interface Console InterfaceSnmp Management Installation Overview Hardware Installation and SetupSafety Overview Recommended Installation Tools Installation into an Equipment RackPower Requirements Environmental RequirementsGbic Interfaces Installing a GbicEquipment Rack Guidelines Connecting Power Installing Optional Hardware ModulesRemoving a Gbic Gbic Care and Handling1 10/100BaseT Ports Cabling Procedures Connecting to the NetworkGigabit Ethernet Ports Cabling Procedures SetupConnecting to a Console Connecting Via the Web Browser Changing the PasswordConnecting Via Telnet Snmp Management IP AssignmentUsing the Stacking Feature IC3524 only Toggle Stacking Enable/Disable Accessing a Submenu ConfigurationLogging General Information Configuration MenuExiting a Submenu Changing System Administration Info System Administration ConfigurationBootstrap Configuration System IP ConfigurationChanging System IP Information Changing Community Strings Snmp ConfigurationAdding or Updating a Trap Receiver Enabling Authentication TrapsDeleting a Trap Receiver Basic Port Configuration Menu appears Port ConfigurationEnabling or Disabling a Port Configuring Auto-NegotiationConfiguring 1000BaseX Ports Configuring a Port ManuallyToggling Port Link Speed Toggling Half to Full DuplexSetting Port Class of Service Advanced Port ConfigurationEnabling or Disabling 802.3x Flow Control Global Port Configuration Setting Port Default PriorityDisplaying the Forwarding Database Unicast Forwarding Database ConfigurationSearching for a MAC Address Setting the MAC Address Age-Out TimeSecurity Management Port Mirroring ConfigurationVlan Management IP Multicast Traffic ManagementSetting the Monitor Port File Up/Downloading ConfigurationImage Downloading through Tftp Performing a Software Upgrade at Runtime Serial Downloading ConfigurationResetting the Switch System Reset ConfigurationPerforming a Software Upgrade System Log Scheduling a System ResetClearing the System Log User Interface ConfigurationSetting Telnet Idle Time-out Period Setting Console Idle Time-out PeriodSystem Utility Changing the PasswordEnabling or Disabling the Web Server Viewing Statistics Advanced Management Configuring Spanning Tree ParametersSpanning Tree Protocol Enabling and Disabling STPSetting Port Priority and Path Cost Spanning Tree Port ConfigurationDuplicated IP Detection and Trap Snmp and Rmon ManagementRmon Management Enabling and Disabling Duplicated IP Detection Enabling and Disabling Station Movement TrapEnabling and Disabling Duplicated IP Trap Viewing a List of Duplicated IP AddressesConfiguring Port New Node Detection Trap Configuring Port SecurityConfiguring Security Level 2 or Level Configuring Port Lock and Intruder LockSetting the Intruder Trap Resetting Security to Defaults Vlan Specifications for the IntraCore 3500 SeriesOther Vlan Features of the switch Inserting/Modifying a Port Trusted MAC AddressKkxxxxxx Kxxxxxxx Configuring Static Vlan GroupsAdvanced Static Vlan Configuration Setting the Port Vlan ID Configuring Vlan Port AttributesSpecifying Tagging or No Tagging for a Port Displaying a Summary of Vlan Groups Configuring Port Receive Frame TypeDisplaying a Vlan Port Summary Adding and Deleting VLANs from the PortMulticast Addresses Resetting Vlan Configuration to DefaultsIgmp Snooping Configuring IP Multicast Traffic ManagementEnabling and Disabling Igmp Snooping Displaying a Summary of Group AddressesAdding Ports to the Selected Address IP Multicast Forwarding Database ConfigurationInserting a Multicast Group Address Removing a Multicast Group Address To remove an addressWeb-Based Management Accessing with a Web BrowserGenl Info General Information Button Front Panel ButtonStatistics Button Port Config Port Configuration Button Span Tree Spanning Tree Button Addr Address Table Button Snmp ButtonVlan Button Port Configuration Creating or Modifying a Vlan Vlan ConfigurationAdding and Deleting Port Members Page Security Button Duplicate IP Button Snmp Management Operations Snmp ManagementSnmp Protocol MIB Tree Community Name and SecurityName Space Path MIB Groups SupportedPage VLANs Switching ConceptsPort-Based VLANs Vlan ID and Tagged FramesHow It Works Port Vlan IDSpanning Tree Parameters Full Duplex, Flow Control and Auto-negotiation Forward DelayFull Duplex Port PriorityAuto-Negotiation Flow ControlProblem Possible Solutions Appendix A. TroubleshootingFeatures Appendix B. Features and SpecificationsSpecifications Technical Support and Warranty Physical CharacteristicsEnvironmental Range Standards ComplianceFCC Compliance Statement Important Safety Instructions Appendix C. FCC Compliance and Warranty StatementsIntraCare Warranty Statement Page Appendix D. Console Port Pin Outs Pin Number Signal NameAppendix E. Online Warranty Registration Bootstrap Configuration Appendix F. BootP ConfigurationImage Banks Loading Software Locally