D-Link DES-5016 Spanning Tree Algorithm, Bridge Priority, Root Cost, Hello Time, Max Age Time

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Fast Ethernet Switching System User’s Guide

Spanning Tree Algorithm

Spanning Tree Algorithm can be enabled or disabled. Use Spanning Tree to prevent network loops.

Bridge Priority

The Bridge Priority can be from 0 to 65535. Zero is the highest Bridge Priority. The higher the Bridge Priority the greater the chance that the DES-5016 will be selected as the Root Bridge. The DES-5016 with the highest Bridge Priority is the Root Bridge.

Root Cost

The Root Cost is the number of times a packet is regenerated before reaching its destination. A source sends a packet to the first device (switch or hub) on the network. When the packet reaches the next hub or switch and is sent out again, the Path Cost becomes two. Each switch and active hub regenerates the packet. To determine the Root Path Cost, count the number of times the packet is regenerated.

The switch with the lowest Path Cost is the Root Bridge. Make the Root Bridge the best switch on the network.

Hello Time

Is the interval between two transmissions of packets sent by the Root Bridge to tell all other switches that it is the Root Bridge. The Hello Time can be set manually, with a range in seconds from 1 to 10. If the Hello Time is set for the switch and the switch is not the Root Bridge then the Hello Time will not take effect until the switch becomes the Root Bridge.

Forward Delay Time

This is the time any port on the DES-5016 spends in the listening state while moving from the listening state to the forwarding state. It can be set from 4 to 30 seconds.

Use the following formula when setting the Hello Time and the Forward Delay Time:

2 x (Forward Delay minus 1 second) > Max Age

2 x (Hello Time plus 1 second) < Max Age

Max Age Time

Is the time a non-root bridge waits for a packet to be sent. At the end of the Max Age, if a packet has not been received from the Root Bridge, the DES-5016 will start sending its own packets and request permission to become the Root Bridge. If it turns out that the DES-5016 has the lowest Bridge Identifier it will become the Root Bridge.

Managing the DES-5016	62

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Contents DES-5016 Fast Ethernet Switching System User’s Guide Link Limited Warranty Hardware SoftwareNorth, Central, and South America Link Offices for Registration and Warranty ServiceEurope and Israel Copyright Statement Wichtige Sicherheitshinweise Table of Contents Page Page Audience About This GuideOrganization Features IntroductionPage Front Panel DES-5016TXDES-5016TF DES-5016TFRear Panel DES-5016 Rear PanelLocal Console Management Management MethodsUpdating Firmware Telnet ManagementInstalling the DES-5016 Unpacking the DES-5016Installation Options Desktop/ Shelf Installation Install Feet on BottomAttach Feet Rack Installation Attach Mounting BracketsInsert into Rack Installing Optional Modules Remove Blank Bracket Insert Optional Module Power On Cable Specifications Connecting the DES-5016 to the NetworkCopper Cable Cable Diagram Fiber Optic Cable Fiber Optic Ports PortsMDI-X Ports RS-232 PortConnecting the DES-5016 to other Switches and Hubs DES-5016 to DES-5016 ConnectionLEDs DES-5016TF LEDsCPU Module PowerDiagnostic StatusLED Act Port TX ModuleLink 100/10Port TX Module LEDs Port FX Module Link/ ActPort 100BASE-FX Module ColLit Dark Port 1000BASE-SX Module Gigabit Module LEDManaging the DES-5016 Local Console Management ∙ Data bits ∙ Parity None ∙ Stop bits ∙ Flow Control NoneTelnet ∙ Default User Name D-Link ∙ Default Password D-Link LogHelp Message Help MessagePanel Conventions Spacebar100BASE-FX/ 1000BASE-SX Switch Port Module System ConfigurationSwitch Port 1-8, 9-16 and Optional Module Configuration Console ProgramVlan Port Management Spanning Tree ConfigurationSnmp Management Configuration Trunking Port ManagementFactory Reset to Default Config Values System Configuration MenuSystem Reset System InformationSystem Information Menu Software UpdateBoot Prom Firmware Version Hardware RevisionSystem Description LAN Default GatewayMAC Address System NameSystem Reset System ResetFactory Reset Factory ResetFactory Reset Confirmation Advantages of Store and Forward System Rate ControlDisadvantages of Store and Forward Advantages of Cut-Through Disadvantages of Cut-ThroughSoftware Update Menu Software Update menuTransfer Firmware Xmodem User Account Management User Account Change MenuAccess Level PasswordConfirm Password Create New UserPage Status Delete UsersDelete Page Old Password Change PasswordNew Password Page Switch Port Configuration State Switch Port Configuration MenuPhysical Priority Port StateFlow Control Spanning Tree Configuration Menu Spanning Tree ConfigurationSTA Operation Levels Bridge Priority Forward Delay TimeSpanning Tree Algorithm Root CostRoot Bridge Root PortSnmp Management Configuration Access Right Snmp Management Configuration MenuSnmp Manager Setting Snmp Community StringCold Start Snmp Trap Manager SettingAuthentication Failure Link Change EventPage Vlan Port Management Vlan Port Management Menu Vlan Port Management menuPort # Create New VlanNew Vlan Name TrunkGroupPage Delete Vlan Menu Vlan NameModify Vlan Menu Virtual LAN NameTrunking Port Management Menu Trunking Port Management menuNew Trunking Group Name Create New Trunking PortName Page Trunking Port Delete Trunking PortModify Trunking Port Trunking Port Name Modify Trunking PortCables TroubleshootingProblem Solution Post Errors Port StatesPage Diagnostic LED Switch Specifications Appendix a DES-5016 Technical SpecificationsPort Specifications Page Fast Ethernet Switching System User’s Guide General EMI Fast Ethernet Switching System User’s Guide Performance Index ActUser Name 52, 54