Administrator Guide

• 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 EMC 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 69. RSTP Default Values
RSTP Parameter Default Value
Forward Delay 15 seconds
Hello Time 2 seconds
Max Age 20 seconds
Port 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 Ethernet interfaces
Port Cost:
• 200000
• 20000
• 2000
• 180000
• 18000
• 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
NOTE:
With large configurations (especially those configurations with more ports) Dell EMC Networking
recommends increasing the hello-time.
The range is from 1 to 10.
The default is 2 seconds.
• Change the max-age parameter.
PROTOCOL SPANNING TREE RSTP mode
max-age seconds
The range is from 6 to 40.
The default is 20 seconds.
To view the current values for global parameters, use the show spanning-tree rstp command from EXEC privilege mode.
Enabling SNMP Traps for Root Elections and Topology
Changes
To enable SNMP traps, use the following command.
• Enable SNMP traps for RSTP, MSTP, and PVST+ collectively.
668
Rapid Spanning Tree Protocol (RSTP)