PROTOCOL SPANNING TREE modemax-age secondsThe range is from 6 to 40.The default is 20 seconds.To view the current values for global parameters, use the show spanning-tree 0 command fromEXEC privilege mode. Refer to the second example in Enabling Spanning Tree Protocol Globally.Modifying Interface STP ParametersYou can set the port cost and port priority values of interfaces in Layer 2 mode.• Port cost — a value that is based on the interface type. The greater the port cost, the less likely theport is selected to be a forwarding port.• Port priority — influences the likelihood that a port is selected to be a forwarding port in case thatseveral ports have the same port cost.The default values are listed in Modifying Global Parameters.To change the port cost or priority of an interface, use the following commands.• Change the port cost of an interface.INTERFACE modespanning-tree 0 cost costThe range is from 0 to 65535.The default values are listed in Modifying Global Parameters.• Change the port priority of an interface.INTERFACE modespanning-tree 0 priority priority-valueThe range is from 0 to 15.The default is 8.To view the current values for interface parameters, use the show spanning-tree 0 command fromEXEC privilege mode. Refer to the second example in Enabling Spanning Tree Protocol Globally.Enabling PortFastThe PortFast feature enables interfaces to begin forwarding traffic approximately 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-violation option causes the interface hardware to be shut down when it receives a BPDU. When youonly implement bpduguard, although the interface is placed in an Error Disabled state when receivingthe BPDU, the physical interface remains up and spanning-tree drops packets in the hardware after aBPDU violation. BPDUs are dropped in the software after receiving the BPDU violation.Spanning Tree Protocol (STP) 873
