Cabletron Systems manual 9E312/9E423 Module Bridging

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9E312/9E423 Module Bridging

In a network design with multiple transparent bridges placed in parallel (i.e., attached to the same local network segment), only a single bridge should forward data through the LAN, leaving the remaining bridges on the segment in a standby state so that another can assume the bridging responsibility (should the currently active bridge go down). The Spanning Tree Algorithm (STA) is the method that bridges use to communicate with each other to ensure that only a single data route exists between any two end stations.

In Transparent bridging, Spanning Tree must be used to prevent data loops (since in an Ethernet environment, a packet propagated down multiple paths would cause higher volumes of trafﬁc and collisions that would cripple a network that relied on carrier sense and collision detection). Spanning Tree selects a controlling Root Bridge and Port for the entire bridged local area network, and a Designated Bridge and Port for each individual network segment. The Root bridge is the one that selects one of two or more available bridge paths between two end stations, basing its decision on factors associated with each of the bridges in the path. A Designated Port/Bridge for a network segment relays frames toward the Root Bridge, or from the Root Bridge onto the network segment. When data passes from one end station to another across a bridged local area network, it is forwarded through the Designated Bridge/Port for each network segment towards the Root Bridge, which in turn forwards frames towards Designated Bridges/Ports on its opposite side.

During the Root Bridge selection process, all bridges on the network communicate STA information via Bridge Protocol Data Units (BPDUs). It is with BPDUs that the bridges collectively determine the current network topology and ensure that all bridges have current topology information.

To access the Bridge Spanning Tree window:

1.From the Bridge Status window, click on . A pull-down menu will appear.

2.Click on Spanning Tree.... The Bridge Spanning Tree window, Figure 3-4, will appear.

3-12	Bridge Spanning Tree

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Contents Page Virus Disclaimer Page Restricted Rights Notice Page Contents 9E312/9E423 Module Bridging IndexIntroduction Introduction Using the 9E312 and 9E423 User’s GuideRelated Manuals Common 9E312 and 9E423 Window Fields Software ConventionsUsing Buttons and Menus Getting Help from Cabletron Systems Technical Support Using On-line HelpGetting Help FTP 9E312 and 9E423 FirmwareIntroduction 9E312 and 9E423 Firmware 9E312/9E423 Module View 9E312/9E423 Module View Viewing Module InformationConnection Status Front Panel InformationMenu Structure Device Menu E312/9E423 Module View Menu StructureBridge Menu Utilities MenuHelp Menu Bridge Port Menu 9E312/9E423 Module Port Status DisplayChassis Manager Window Viewing the Device Type Setting the Device Date and TimeManaging the Module Edit Time Window Enabling and Disabling Bridge Ports Using the Find Source Address FeatureFind Source Address Window Summary InformationDescription Interface Description FieldsIndex TypeRaw Counts Interface Performance Statistics/Bar GraphsRate Interface Detail WindowLoad Unicast Interface Detail Window StatisticsUnknown Protocol ErrorMulticast DiscardedMaking Sense of Interface Statistics Testing and Disabling the Current InterfacePackets Received Packets TransmittedUsing the Applications Pull-down menu 9E312/9E423 Module View Summary Information Bridging Basics 9E312/9E423 Module BridgingMore on Transparent Bridging An Overview of Remote Bridge ManagementBridge Status Window Bridge State on Interface Bridge Status Window Information FieldsInterface Speed Interface TypeInterface Address Bridge Statistics Enabling and Disabling BridgingPerformance Graphs Filtered Magenta Errors RedBridge Performance Graph Window Fields Frames Forwarded GreenConﬁguring the Bridge Performance Graphs Interface Statistics WindowAddress Interface Statistics Window FieldsNon-Unicast Bridge Spanning Tree9E312/9E423 Module Bridging Bridge Priority Conﬁguring the Bridge Spanning Tree WindowBridge Level Fields Protocol Root BridgeRoot Cost Root PortBridge Port Level Fields Designated Bridge Path CostDesignated Cost Designated RootChanging the Spanning Tree Algorithm Protocol Type Changing Bridge Spanning Tree ParametersChanging Bridge Priority Changing Max Age Time Changing Forwarding Delay TimeChanging Hello Time Changing Path Cost Filtering DatabaseChanging Port Priority 9E312/9E423 Module Bridging Filtering Database Window Capacity Filtering Database Window FieldsList NumberPort Filtering Conﬁguring the Filtering DatabaseSource Port Receive PortChanging the Receive Port Altering the Ageing TimeChanging the Type of Entry Adding or Deleting Individual Entries Changing the Port Filtering ActionClearing All Permanent, Static, or Dynamic Entries Using Port Source AddressingDevice Ageing Time Window Setting the Ageing TimeDuplex Modes Window Duplex ModesFull Duplex Duplex Modes Window FieldsInterface Setting the Duplex Mode Index Index-2