776 | Rapid Spanning Tree Protocol (RSTP)w w w . d e l l . c o m | s u p p o r t . d e l l . c o m Table 38-2 displays the default values for RSTP.To change these parameters, use the following commands, on the root bridge:View the current values for global parameters using the show spanning-tree rstp command from EXECprivilege mode. See Figure 38-5.Modify Interface ParametersOn interfaces in Layer 2 mode, you can set the port cost and port priority values.• Port cost is a value that is based on the interface type. The default values are listed in Table 38-2. Thegreater the port cost, the less likely the port will 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.Table 38-2. RSTP Default ValuesRSTP Parameter Default ValueForward Delay 15 secondsHello Time 2 secondsMax Age 20 secondsPort Cost 100-Mb/s Ethernet interfaces 2000001-Gigabit Ethernet interfaces 2000010-Gigabit Ethernet interfaces 2000Port Channel with 100 Mb/s Ethernet interfaces 180000Port Channel with 1-Gigabit Ethernet interfaces 18000Port Channel with 10-Gigabit Ethernet interfaces 1800Port Priority 128Task Command Syntax Command ModeChange the forward-delay parameter.• Range: 4 to 30• Default: 15 secondsforward-delay seconds PROTOCOLSPANNING TREERSTPChange the hello-time parameter.Note: With large configurations (especially those with more ports) DellForce10 recommends that you increase the hello-time.Range: 1 to 10Default: 2 secondshello-time seconds PROTOCOLSPANNING TREERSTPChange the max-age parameter.Range: 6 to 40Default: 20 secondsmax-age seconds PROTOCOLSPANNING TREERSTP
