Moxa Technologies PT-7728 How STP Works, STP Requirements, STP Calculation, STP Configuration

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PT-7728 User’s Manual

Featured Functions

How STP Works

When enabled, STP determines the most appropriate path for traffic through a network. The method is described below:

STP Requirements

Before STP can configure the network, the system must satisfy the following requirements:

yCommunication must be established between all bridges. This communication is carried out using Bridge Protocol Data Units (BPDUs), which are transmitted in packets with a known multicast address.

yEach bridge must have a Bridge Identifier that specifies which bridge acts as the central reference point, or Root Bridge, for the STP system. Bridges with a lower Bridge Identifier are more likely to be designated as the Root Bridge. The Bridge Identifier is calculated using the MAC address of the bridge and a priority defined for the bridge. The default priority of PT-7728 is 32768.

yEach port has a cost that specifies the efficiency of each link. The efficiency cost is usually determined by the bandwidth of the link, with less efficient links assigned a higher cost. The following table shows the default port costs for a switch:

Port Speed

Path Cost 802.1D,

Path Cost

 

1998 Edition

802.1w-2001

10 Mbps

100

2,000,000

100 Mbps

19

200,000

1000 Mbps

4

20,000

STP Calculation

The first step of the STP process is to perform calculations. During this stage, each bridge on the network transmits BPDUs. The following items will then be calculated:

yThe bridge that will act as the Root Bridge. The Root Bridge is the central reference point from which the network is configured.

yThe Root Path Costs for each bridge. This is the cost of the paths from each bridge to the Root Bridge.

yThe identity of each bridge’s Root Port. The Root Port is the port on the bridge that connects to the Root Bridge via the most efficient path. In other words, this port connects to the Root Bridge via the path with the lowest Root Path Cost. The Root Bridge itself does not have a Root Port.

yThe identity of the Designated Bridge for each LAN segment. The Designated Bridge is the bridge with the lowest Root Path Cost from that segment. If several bridges have the same Root Path Cost, the one with the lowest Bridge Identifier becomes the Designated Bridge. Traffic transmitted in the direction of the Root Bridge will flow through the Designated Bridge. The port on this bridge that connects to the segment is called the Designated Bridge Port.

STP Configuration

After all the bridges on the network agree on the identity of the Root Bridge and all relevant parameters have been established, each bridge is configured to forward traffic only between its Root Port and the Designated Bridge Ports for their respective network segments. All other ports are blocked, which means that they will not be allowed to receive or forward traffic.

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Contents First Edition, February Moxa Inc Moxa PowerTrans Switch PT-7728 User’s ManualTrademarks Copyright NoticeDisclaimer Table of Contents Appendix a MIB Groups Appendix B Specifications Introduction ‰ Overview ‰ Package Checklist ‰ Software FeaturesSoftware Features Package ChecklistOverview Getting Started Serial Console Configuration 115200, None, 8, 1, VT100 PT-7728 User’s Manual Getting Started Key Function Configuration by Telnet ConsolePT-7728 User’s Manual Getting Started PT-7728 User’s Manual Getting Started Configuration by Web Browser Disabling Telnet and Browser Access Featured Functions System Identification Configuring Basic SettingsPassword PasswordAccount Hosts That Need Access Input Format Accessible IPGrant access to one host with a specific IP address Grant access to any host on a specific subnetworkName EnablePort DescriptionSpeed NetworkFDX Flow Ctrl Default Gateway Auto IP ConfigurationSwitch IP Address Switch Subnet MaskCurrent Date TimeDaylight Saving Time Current TimeSystem File Update-By Remote Tftp Log Files Path and Name Configuration Files Path and NameTftp Server IP/Name Firmware Files Path and NameFactory Default System File Update-By Local Import/ExportPort Trunking Concept Using Port TrunkingAvailable Ports/Member Ports Configuring Port TrunkingTrunk Group Maximum of 4 trunk groups Trunk TypeSetting Description Configuring SnmpTrunk Table V1, V2c Write/Read Community Snmp Read/Write SettingsSnmp Versions V1, V2c Read Community1st Trap Server IP/Name Setting Description Factory Default Setting Description Factory DefaultPrivate MIB information Using Communication RedundancyTurbo Ring Concept Initial setup for Turbo Ring or Turbo RingTurbo Ring with odd number switches Determining the Redundant Path for Turbo Ring Ring Coupling ConfigurationSwitch B Dual-Homing Configuration for Turbo Ring Configuring Turbo Ring and Turbo RingConfiguring Turbo Ring Set as Master Now ActiveMaster/Slave Redundancy ProtocolCoupling Port Enable Ring CouplingCoupling Control Port Coupling-Mode Enable RingRing 1/2-Status Ring 1/2-1st Ring Port Status Ring 1/2-2nd Ring Port Status Primary/Backup Port Coupling ModeSTP/RSTP Concept What is STP?PT-7728 User’s Manual Featured Functions Port Speed Path Cost 802.1D Edition 802.1w-2001 STP ConfigurationHow STP Works STP RequirementsDifferences between Rstp and STP STP ReconfigurationSTP Example Using STP on a Network with Multiple VLANs Bridge Priority Configuring STP/RSTPRoot/Not Root Protocol of RedundancyMax. Age sec Forwarding DelayEnable STP per Port Hello Time secTraffic Prioritization Concept Using Traffic PrioritizationConfiguration Limits of RSTP/STP What is Traffic Prioritization?Ieee 802.1p Priority Level Ieee 802.1D Traffic Type How Traffic Prioritization WorksTraffic Prioritization Differentiated Services DiffServ Traffic MarkingTraffic Queues Inspect TOS Configuring Traffic PrioritizationQoS Classification Queuing MechanismInspect COS Setting Description FactoryCoS Mapping TOS/DiffServ MappingWhat is a VLAN? Using Virtual LANVirtual LAN Vlan Concept Communication Between VLANs VLANs and the PowerTransBenefits of VLANs Managing a VlanVLANs Tagged and Untagged Membership Sample Applications of VLANs using PT-7728PT-7728 User’s Manual Featured Functions Port Type Configuring Virtual LANVlan Settings Management Vlan IDVlan Table Using Multicast FilteringWhat is an IP Multicast? Concept of Multicast FilteringMulticast Filtering Benefits of MulticastNetwork without multicast filtering Network with multicast filtering Multicast Filtering and Moxa PowerTrans SwitchIgmp Internet Group Management Protocol Snooping Mode Query ModeStatic Multicast MAC Configuring Igmp SnoopingIgmp Multicast Filtering Gmrp Garp Multicast Registration ProtocolIgmp Snooping Settings Add Static Multicast MAC Gmrp Table Using Bandwidth ManagementConfiguring Gmrp Gmrp enableTraffic Rate Limiting Settings Configuring Bandwidth Management Broadcast Storm ProtectionIngress Ieee Using Port Access ControlConfiguring Static Port Lock Static Port LockServer Port Configuring IeeeDatabase Option Radius ServerLocal User Database Setup 802.1X Re-AuthenticationPort Access Control Table Using Auto WarningLocal User Database Setup Event Type Configuring Email WarningMail Server IP/Name Email SetupMoxaPowerTransSwitch0001@SwitchLocation Port EventsEmail Address Configuring Relay WarningPassword Setting Account NameEvent Setup Override relay alarm settings Using Line-Swap-Fast-RecoveryUsing Set Device IP Configuring Line-Swap Fast RecoverySet up the connected devices Configuring Set Device IPMirror Port Using DiagnosisMonitor by Switch Using MonitorPing Monitor by Port Using the MAC Address TableMAC Using Event LogSyslog Server Using SyslogPT-7728 User’s Manual Featured Functions MIB II.5 Icmp Group MIB II.1 System GroupMIB II.2 Interfaces Group MIB II.4 IP GroupMIB II.11 Snmp Group MIB II.10 Transmission GroupMIB II.17 dot1dBridge Group Private Traps Public TrapsTechnology Switch PropertiesInterface Optical Fiber 100BaseFX PowerMechanical WarrantyEnvironmental
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