Modifying Global Parameters - Dell S4820T Configuration Manual

Modifying Global Parameters

The root bridge sets the values for forward-delay, hello-time, max-age, and max-hops and overwrites the
values set on other MSTP bridges.
• 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 MSTP bridge protocol data units (BPDUs).
• Max-age — the length of time the bridge maintains configuration information before it refreshes that
information by recomputing the MST topology.
• Max-hops — the maximum number of hops a BPDU can travel before a receiving switch discards it.
NOTE: Dell Networking recommends that only experienced network administrators change MSTP
parameters. Poorly planned modification of MSTP parameters can negatively affect network
performance.
To change the MSTP parameters, use the following commands on the root bridge.
1. Change the forward-delay parameter.
PROTOCOL MSTP mode
forward-delay seconds
The range is from 4 to 30.
The default is 15 seconds.
2. Change the hello-time parameter.
PROTOCOL MSTP mode
hello-time seconds
NOTE: With large configurations (especially those configurations with more ports) Dell
Networking recommends increasing the hello-time.
The range is from 1 to 10.
The default is 2 seconds.
3. Change the max-age parameter.
PROTOCOL MSTP mode
max-age seconds
The range is from 6 to 40.
The default is 20 seconds.
4. Change the max-hops parameter.
PROTOCOL MSTP mode
max-hops number
The range is from 1 to 40.
652
Multiple Spanning Tree Protocol (MSTP)