Modifying Global ParametersYou can modify RSTP parameters.The root bridge sets the values for forward-delay, hello-time, and max-age and overwrites the values seton other bridges participating in the Rapid Spanning Tree group.• Forward-delay — the amount of time an interface waits in the Listening state and the Learning statebefore it transitions to the Forwarding state.• Hello-time — the time interval in which the bridge sends RSTP BPDUs.• Max-age — the length of time the bridge maintains configuration information before it refreshes thatinformation by recomputing the RST topology.NOTE: Dell Networking recommends that only experienced network administrators change theRapid Spanning Tree group parameters. Poorly planned modification of the RSTP parameters cannegatively affect network performance.The following table displays the default values for RSTP.Table 77. RSTP Default ValuesRSTP Parameter Default ValueForward Delay 15 secondsHello Time 2 secondsMax Age 20 secondsPort Cost:• 100-Mb/s Ethernet interfaces• 1-Gigabit Ethernet interfaces• 10-Gigabit Ethernet interfaces• Port Channel with 100 Mb/s Ethernet interfaces• Port Channel with 1-Gigabit Ethernet interfaces• Port Channel with 10-Gigabit EthernetinterfacesPort Cost:• 200000• 20000• 2000• 180000• 18000• 1800Port Priority 128To change these parameters, use the following commands.• Change the forward-delay parameter.PROTOCOL SPANNING TREE RSTP modeforward-delay secondsThe range is from 4 to 30.The default is 15 seconds.• Change the hello-time parameter.PROTOCOL SPANNING TREE RSTP modehello-time secondsRapid Spanning Tree Protocol (RSTP) 765
