Allied Telesis AT-GS950/8 manual Port Speed Port Cost

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Chapter 8: Spanning Tree Protocol (STP)

a bridge participating in STP has a cost associated with it. The cost of a port on a bridge is typically based on port speed. The faster the port, the lower the port cost. The exception to this is the ports on the root bridge, where all ports have a port cost of 0.

Path cost is simply the sum of the port costs between a bridge and the root bridge.

The AT-GS950/8 WebSmart switch automatically sets the port cost according to the speed of the port, assigning a lower value for higher speeds. Table 6 lists the STP port costs.

Table 4. STP Port Costs

Port Speed	Port Cost


10 Mbps	100

100 Mbps	10

1000 Mbps	4

Table 5 lists the STP port costs with Auto when a port is part of a port trunk.

Table 5. STP Auto-Detect Port Trunk Costs

Port Speed	Port Cost


10 Mbps	4

100 Mbps	4

1000 Mbps	2

Table 6 lists the RSTP port costs with Auto.

Table 6. RSTP Auto Port Costs

Port Speed	Port Cost


10 Mbps	2,000,000

100 Mbps	200,000

1000 Mbps	20,000

Table 7 lists the RSTP port costs with Auto when the port is part of a port

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Contents Management Software Page Contents Contents Figures Figures Preface Where to Find Web-based Guides Management Software Updates Contacting Allied TelesisPreface Getting Started ChapterStarting a Management Session Main Save Configuration Click Apply Saving ChangesQuitting a Management Session Getting Started Basic Switch Parameters Basic Switch Parameters AT-S82 Management Software User’s Guide Disabled EnabledDisabling or Enabling Ping Blocking Enabling or Disabling 802.1X Forwarding Control Changing the Administrator’s Password Rebooting the Switch Resetting the Switch and Retaining the IP Address Reset Click Apply Switch is resetAT-S82 Management Software User’s Guide Downloading New Firmware Download Status MessagePort Configuration Configuring Port Parameters Port is enabled. This is the default Copper FiberTrunking Trunking Overview Trunking Guidelines Trunking AlgorithmAT-S82 Management Software User’s Guide Configuring the Trunking Algorithm DAxorSASetting up the Trunk Port Trunking ConfigurationTrunking Port Mirroring Port Mirroring Overview Configuring Port Mirroring Port Mirroring VLANs Vlan Features Increased Performance Improved Manageability SecurityAT-S82 Management Software User’s Guide Vlan Overview Vlan Identifier Vlan Port MembersIncoming Outgoing Tagged Untagged Frames Guidelines for Creating a Vlan Working with VLANs Vlan DetailDisplaying all VLANs Click Show All Static Vlan EntriesVlan Protected Ports Vlan Protected Ports Vlan ExampleAT-S82 Management Software User’s Guide VLANs Class of Service Class of Service Overview Mapping Ports to Egress QueuesIeee 802.1p Priority Level Port Priority Queue Port Egress Queue Maximum Number Packets Mapping Priorities to Queues Setting Up the Schedule Assigning Priority to Ports Class of Service Spanning Tree Protocol STP Spanning Tree Overview Bridge Priority RootPath Costs and Port Costs Increment Bridge PriorityPort Speed Port Cost Port Priority Increment Port PriorityHello Time and Bridge Protocol Data Units BPDUs Point-to-Point and Edge Ports Edge Port Spanning Tree and VLANs Spanning Tree Protocol STP Configuring Spanning Tree Rstp STP CompatibleDisabled Configuring STP Port Settings Yes FalseTrue AutoSpanning Tree Protocol STP

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