Bridging Basics, About Transparent Bridging | Cabletron Systems 2.2

Chapter 2

Bridging

About bridging methods; viewing and managing bridging interfaces; using the Bridge Status window; viewing bridge statistics; using Spanning Tree; using the Filtering Database; conﬁguring duplex modes; using the Interface Conﬁguration window; and setting Bridge Translation

Bridging Basics

Bridges are used in local area networks to connect two or more network segments and to control the ßow of packets between the segments. Ideally, bridges forward packets to another network segment only when necessary.

Bridges are also used to increase the fault tolerance in a local area network by creating redundant bridge paths between network segments. In the event of a bridge or bridge segment failure, an alternate bridge path will be available to network trafÞc, without signiÞcant interruption to its ßow.

The method a bridge uses to forward packets, choose a bridge path, and ensure that a sending stationÕs messages take only one bridge path depends on the bridgeÕs type: Transparent (generally used in Ethernet or FDDI environments) or Source Routing (generally used in Token Ring environments), source routing-transparent, or source route-transparentÑthe two latter being combinations that are found in a mixed network environment.

About Transparent Bridging

Transparent bridges are most common in Ethernet networks. Individual Transparent bridges monitor packet trafÞc on attached network segments to learn where end stations reside in relation to each segment by mapping the Source Address of each received frame to the port (and segment) it was detected on. This information gets stored in the bridgeÕs Filtering Database.

When in the Forwarding state, the bridge compares a packetÕs destination address to the information in the Filtering Database to determine if the packet should be forwarded to another network segment or Þltered (i.e., not forwarded). A bridge

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Cabletron Systems 2.2 manual Bridging Basics, About Transparent Bridging

Contents

Bridge/Router Interface Brim User’s Guide Page Virus Disclaimer Restricted Rights Notice Contents Contents Index Chapter Fddi ApplicationsChapter WAN Applications Chapter ATM Conﬁguration Contents Introduction BRIM-E100 Using the Brim User’s Guide Brim Management Applications Related Manuals Software Conventions Using the Mouse Left Mouse Button Right Mouse Button Location Common Device Window FieldsDevice Name IP Address Using Window Buttons Accessing On-line Documentation Using On-line HelpGetting Help Hours a day, 365 days a year Getting Help from the Cabletron Systems Global Call Center Introduction Getting Help About Transparent Bridging Bridging Basics Bridging About Source Route Bridging About Source Route-Transparent Bridges About Source Route-Translational Bridges Viewing and Managing Bridging Interfaces Bridging Bridge Status Window Up Time Bridge Status Window Bridge Address Accessing Bridge Status Window OptionsBridge State on Interface Interface Type Bridging Bridging Bridging Bridging Enabling and Disabling Bridging Enabling and Disabling All Installed InterfacesEnabling and Disabling Individual Interfaces Performance Graphs Bridge Statistics Bridging Xmitted Blue Errors RedFrames Forwarded Green Filtered Magenta Bridge Detail Breakdown Xmitted ErrorsFrames Forwarded Filtered Forwarded to Interface StatisticsForwarded from Address DescriptionType Discarded ErrorUnicast Non-Unicast Csmacd Statistics Receive Errors Transmission Errors PPP Link Statistics Collision Errors Errors Statistics Dot5 Errors Burst Errors Line Errors Soft Errors Internal ErrorsCongestion Errors Token Errors Source Route Statistics Received Frames Discards Transmitted Frames Spanning Tree Bridge Priority Bridge Level Protocol Root BridgeRoot Cost Root Port Bridge Port Level Designated Bridge Path CostDesignated Cost Designated Root Changing Bridge Priority Conﬁguring Spanning TreeChanging the Spanning Tree Algorithm Protocol Type Changing Hello Time Changing Forwarding Delay TimeChanging Max Age Time Changing Port Priority Filtering DatabaseChanging Path Cost Bridging 11. The Filtering Database Window Aging Time ListNumber Capacity Port Filtering Conﬁguring the Filtering DatabaseAltering the Aging Time Adding or Deleting Individual Entries Changing the Type of EntryChanging the Receive Port Changing the Port Filtering Action Clearing All Permanent, Static, or Dynamic Entries Special Filter Databases Ethernet and Token Ring Special Filter Database Windows Special Filter Database Window EnableFile Data Offset Destination AddressSource Address Data Type Deﬁning and Editing Filters in the Special Database Changing the Receive Ports Setting the Port Filtering ActionChanging the Port Filtering Action Saving a Set of Filters to a File Enabling and Disabling a FilterClearing the Port Filtering Action Interface Conﬁguration Transparent Bridge MethodsSource Routing Source Route Transparent Setting the Bridge MethodNetBIOS Protocol Transmission Methods 16. Source Route ConÞguration Window Source Route Conﬁguration Source Route Conﬁguration Source Routing Information Subnet Mask Spanning Tree Expl Local SegmentTarget Segment Hop Count Limit Bridge Number Spanning Tree Mode Making and Setting Changes Using the Find Source Address Feature Using the Port Source Addresses Window Setting the Aging Time Using the Token Ring Bridge and Port Conﬁguration Windows Bridging Ring Number Virtual Ring Number Bridge Mode/Explorer Type Port ModeNovell Translation Ring Speed Source Route/STE Duplex Modes Interface Duplex Modes WindowFull Duplex Ethernet Port Conﬁguration Setting the Duplex Mode Fast Ethernet Port Conﬁguration Standard Mode Bridging Link State Current Operational ModeDesired Operational Mode Port Type Setting the Operational Mode for the FE-100TX Sonet Port Conﬁguration Setting the Operational Mode for the FE-100FXSONET/SDH Conﬁguration Sonet SONET/SDH Statistics Bridging 26. The SONET/SDH Statistics Window Errors Statistics Bridging 27. The SmartTrunk ConÞguration and Status Window Conﬁguring SmartTrunking SmartTrunk State PortName Mode Bridging Conﬁguring Broadcast Suppression Token Ring Bridge Mode Setting Token Ring Bridge Mode Setting Bridge Translation 32. Bridge Translation Window Enabling and Disabling Auto and Dual Translate Modes Conﬁguring Novell Token Ring Packet Translation Conﬁguring Token Ring Packet Translation IBM Translation Table State Index Conﬁguring Snap Translation Snap Translation Table Using the Novell Translation Window Bridging Ethernet Port Physical View Using the Physical View Windows for the Etwmim Epim Type Active Port 41. Token Ring Port Physical View Token Ring Port Physical View FNB State Ring State Active Monitor Bridging 104 Using the Physical View Windows for the Etwmim Fddi Applications Conﬁguration Window Accessing the Fddi Menu MAC State Concentrator M Ports SMT VersionReq. Requested Target Token Rotation Time Neg. Negotiated MAC Path Connection Policy WindowConcentrator Non-M Ports Number of MACs Connection Policy Window 15 32,768 Ð a permanently set value for this bit Station List Window Address ModeNumber of Nodes Upstream Neighbor Node Class Transmit Frames Fddi Performance WindowReceive Frames Frame Errors Setting the Time IntervalRing Ops Fddi Applications Fddi Performance Window WAN Applications Accessing the WAN Status Windows Current Active Viewing WAN Interface StatusCurrent Primary Desired Primary Conﬁguring the Synchronous Connection State Change InspeedOutspeed Clock Source Line Coding Conﬁguring T-1 PortsWAN Port Name Line Type Xmt Clock Source Loopback ModeSignal Mode Circuit ID Interface LineCoding Using the T1 FracTable Conﬁguration Window Max Bandwidth ChannelsConﬁguring the Fractional Table Changing the Interface Line Coding Restoring a Fractional Table Compression Displaying the WAN Logical View CRC Length Changing WAN Logical Settings Synchronous Admin/Status Viewing the WAN Port Admin/StatusOperational Status WAN Interfaces T1 Admin/StatusAdmin Status Oper and Admin Enabling and Disabling WAN T1 Interfaces Displaying Synchronous Port StatisticsFrame Check Interrupted Frames Total ErrorsXmit UnderRuns Receive OverRuns WAN Applications Displaying Synchronous Port Statistics ATM Conﬁguration Accessing the ATM Connections Window Connection Data Settings VPI Conﬁguring Connections Adding a New Connection Deleting a Connection ATM Conﬁguration Conﬁguring Connections Index Index-2 Index-3 Index-4 Index-5 Index Index-6