Modifying Global Parameters - Dell S4820T Configuration Manual

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 68. RSTP Default Values
RSTP Parameter
Forward Delay
Hello Time
Max Age
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 Priority
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)
Default Value
15 seconds
2 seconds
20 seconds
Port Cost:
• 200000
• 20000
• 2000
• 180000
• 18000
• 1800
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