Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 789

Modifying Global Parameters You can modify RSTP parameters. The root bridge sets the values for forward-delay, hello-time, and max-age and overwrites the values set on 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 state before 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 that information by recomputing the RST topology. NOTE: Dell Networking recommends that only experienced network administrators change the Rapid Spanning Tree group parameters. Poorly planned modification of the RSTP parameters can negatively affect network performance. The following table displays the default values for RSTP. Table 63. RSTP Default Values RSTP Parameter Default Value Forward Delay 15 seconds Hello Time 2 seconds Max Age 20 seconds Port Cost: Port Cost: • 100-Mb/s Ethernet interfaces • 200000 • 1-Gigabit Ethernet interfaces • 20000 • 10-Gigabit Ethernet interfaces • 2000 • Port Channel with 100 Mb/s Ethernet interfaces • 180000 • Port Channel with 1-Gigabit Ethernet interfaces • 18000 • Port Channel with 10-Gigabit Ethernet interfaces • 1800 Port Priority 128 To change these parameters, use the following commands. • Change the forward-delay parameter. PROTOCOL SPANNING TREE RSTP mode forward-delay seconds The range is from 4 to 30. The default is 15 seconds. • Change the hello-time parameter. PROTOCOL SPANNING TREE RSTP mode hello-time seconds Rapid Spanning Tree Protocol (RSTP) 789