Cabletron Systems 9A128-01 manual Hello Time, Max Age, Forwarding Delay, Hold Time, Priority

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Bridging

Hello Time

This parameter indicates, in seconds, the length of time the Root Bridge (or bridge attempting to become the Root) waits before resending Configuration BPDUs. The range for this field is 1 to 10 seconds, with a default value of 2 seconds. The Root Bridge sets the Hello Time.

Max Age

This parameter displays the bridge’s BPDU ageing timer. This controls the maximum time a BPDU can be retained by the bridge before it is discarded. During normal operation, each bridge in the network receives a new Configuration BPDU before the timer expires. If the timer expires before a Configuration BPDU is received, it indicates that the former Root is no longer active. The remaining bridges begin Spanning Tree operation to select a new Root. The current Root Bridge on the network sets the Max Age time. The range for this field is 6 to 40 seconds, with a default value of 20 seconds.

Forwarding Delay

This parameter displays the time period which elapses between states while the bridge is moving to the Forwarding state. For example, while moving from a Blocking to a Forwarding state, the port first moves from Blocking to Listening to BPDU activity on the network, remains there for the Forward Delay period, then moves to the Learning State (and remains in it for the Forward Delay period), and finally moves into a Forwarding state. This timer is set by the Root Bridge. During a topology change, the Forward Delay is also used as the Filtering Database Aging Time (refer to Filtering Database, page 5-21), which ensures that the Filtering Database maintains current topology information.

Hold Time

This parameter displays, in seconds, the minimum time that can elapse between the transmission of Configuration BPDUs through a bridge port. The Hold Time ensures that Configuration BPDUs are not transmitted too frequently through any bridge port. Receiving a BPDU starts the Hold Timer. After the Hold Timer expires, the port transmits its Configuration BPDU to send configuration information to the Root. The Hold Time is a fixed value, as specified by the IEEE 802.1d specification.

The following fields are applicable to each bridge port on the selected module:

Priority

If two or more ports on the same bridge are connected to the same LAN segment, they will receive the same Root ID/Root Cost/Bridge ID information in Configuration BPDUs received at each port. In this case, the BPDU’s Port ID information – the transmitting port’s identifier and its manageable Priority component – is used to determine which is the Designated Port for that segment.

A lower assigned value gives the port a higher Priority when BPDUs are compared. The allowable range is 0-FF hexadecimal (0-255 decimal); the default is 80 hexadecimal.

Bridge Spanning Tree

5-17

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Contents Cabletron Systems Virus Disclaimer Page Restricted Rights Notice Page Contents Chapter Bridging Chapter Fddi ManagementIndex Using This Guide IntroductionRelated Reading Device Name Software ConventionsCommon Window Fields IP AddressGetting Help Using ButtonsUsing On-line Help LocationGetting Help from the Cabletron Systems Global Call Center FTPFirmware Versions Supported 9A128-01 Module View Viewing Module Information Front Panel InformationUpTime Boot PromConnection Status Port StatusTime Menu StructureDate A128-01 Module View Menu Structure Device MenuPort Status Menu Help Menu Fddi MenuUtilities Menu Board MenusPort Status Displays Port MenusSelecting a Port Status View Bridge Port Status DisplaysBridge Port Status Color Codes Bridge Port StateBridge Mapping Fddi Port Status DisplaysConnection State LER EstimateChassis Manager Window Fddi Port Status Color CodesDevice Type Viewing Hardware TypesModule Type Viewing I/F Summary Information Module Type WindowSta IndexDescription Interface Performance Statistics/Bar GraphsRaw Counts LoadRate Interface Statistics WindowUnicast ErrorAddress Non-UnicastTransmit Queue Size Transmit only Using the Find Source Address FeaturePackets Received Received only Packets Transmitted Transmit onlySetting the Device Date and Time Managing the HubEnabling and Disabling Ports Bridge PortsModule Ports Accessing the ATM Connections Window ATM ConfigurationATM Configuration Connection DataSettings VPIConfiguring Connections Adding a New ConnectionDeleting a Connection ATM Configuration Configuring Connections Fddi Management Configuration Fddi ManagementMAC State Req. Requested Target Token Rotation Time SMT VersionNeg. Negotiated Number of MACs Concentrator M PortsConcentrator Non-M Ports MAC PathConnection Policy 15 32,768 a permanently set value for this bit Station List Address ModeNumber of Nodes Topology Stations PanelNode Class Upstream NeighborPerformance Receive Frames Frame ErrorsTransmit Frames Lost FramesFddi Management Performance Bridging Bridge Status Window BridgingInterface Type Up TimeBridge State on Interface Bridge AddressConfiguring Duplex Modes Enabling and Disabling Bridging Bridge Statistics Performance GraphsForwarded Green Xmitted Blue Total Errors RedFiltered Magenta Configuring the Bridge Performance GraphsFiltered ErrorsForwarded XmittedForwarded to Interface Statistics WindowForwarded from Description Using Source Addressing Setting the Ageing Time Port Source Addresses WindowBridge Spanning Tree Configuring the Bridge Spanning Tree Window Bridge PriorityRoot Port Root BridgeRoot Cost ProtocolMax Age Forwarding DelayHello Time Hold TimeChanging Bridge Spanning Tree Parameters Changing the Spanning Tree Algorithm Protocol Type Changing Bridge PriorityChanging Hello Time Changing Max Age Time Changing Forwarding Delay TimeChanging Port Priority Filtering Database Changing Path CostBridging Bridging Capacity ListNumber Ageing TimeReceive Port Configuring the Filtering DatabasePort Filtering Changing the Receive Port Altering the Ageing TimeChanging the Type of Entry Changing the Port Filtering ActionClearing All Permanent, Static, or Dynamic Entries Bridging Filtering Database Index Index-2 Index-3 Index Index-4
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