Switch 7700 Command reference Guide, v2.0

MSTP Configuration Commands 341
MSTP provides Root protection function to protect the root bridge: The port
configured with Root protection only plays a role of designated port on every
instance. Whenever such port receives a higher-priority BPDU, it will be set to
listening state and not forward packets any more (as if the link to the port is
disconnected). If the port has not received any higher-priority BPDU for a certain
period of time thereafter, it will resume the normal state.
Related command: stp interface root-protection.
Example
Enable Root protection on the Ethernet5/0/1 port of the switch.
[SW7700-Ethernet5/0/1]stp root-protection
stp timer forward-delay Syntax
stp timer forward-delay centi-seconds
undo stp timer forward-delay
View
System view
Parameter
centi-seconds: Specifies Forward Delay, ranging from 400 to 3000 and
measured in centiseconds. By default, the Forward Delay of the switch is 1500
centiseconds.
Description
■ Use the stp timer forward-delay command to configure Forward Delay for
the switch.
■ Use the undo stp timer forward-delay command to restore the default
Forward Delay.
To avoid a temporary loop, MSTP defines a medium state, Learning, when the port
switches from the Discarding state to Forwarding state. There is also a delay before
state switchover to guarantee the synchronous switchover with the remote switch.
The Forward Delay configured on the root bridge determines the state transition
time.
The root bridge will determine the state transition time according to the
configured values, while the other switches will apply the forward delay
configured on it.
When configuring Hello time, Forward Delay and Max Age, please guarantee the
following equations:
2 * (Forward Delay - 1.0 seconds) >= Max Age
Max Age >= 2 * (Hello Time + 1.0 seconds)
Only if the above-mentioned formulas are equal can the MSTP normally operate
on the entire network, otherwise, the network may flap frequently. You are
recommended to use the stp instance root primary command to specify the