1056 | Spanning Tree Protocolw w w . d e l l . c o m | s u p p o r t . d e l l . c o m View the current values for global parameters using the show spanning-tree 0 command from EXECprivilege mode. See Figure 52-5.Modifying Interface STP ParametersYou can set the port cost and port priority values of interfaces in Layer 2 mode.• Port cost is a value that is based on the interface type. The greater the port cost, the less likely the portwill be selected to be a forwarding port.• Port priority influences the likelihood that a port will be selected to be a forwarding port in case thatseveral ports have the same port cost.The default values are listed in Table 52-2.To change the port cost or priority of an interface:View the current values for interface parameters using the show spanning-tree 0 command from EXECprivilege mode. See Figure 52-5.Enabling PortFastThe PortFast feature enables interfaces to transition to a forwarding state and start to transmit trafficapproximately 30 seconds sooner.Interfaces forward frames by default until they receive a BPDU that indicates that they should behaveotherwise; they do not go through the Learning and Listening states. The bpduguard shutdown-on-violationoption causes the interface hardware to shut down when it receives a BPDU. When only bpduguard isconfigured, although the interface is placed in an Error Disabled state when receiving the BPDU, thephysical interface remains up and spanning-tree will drop packets in the hardware after a BPDU violation.BPDUs are dropped in the software after receiving the BPDU violation.Task Command Syntax Command ModeChange the port cost of an interface.Range: 0 to 65535Default: see Table 52-2.spanning-tree 0 cost cost INTERFACEChange the port priority of an interface.Range: 0 to 15Default: 8spanning-tree 0 prioritypriority-valueINTERFACECaution: Enable PortFast only on links connecting to an end station. PortFast can cause loops if it is enabled on aninterface connected to a network.
