User's Manual

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root port and designated port starts data forwarding immediately, temporary loop may be caused. To solve this
problem, RSTP adopts a state removal mechanism. Before the root port and the designated port begin to
forward data, an intermediate state must be experienced. The intermediate state changes into the forwarding
state after the forward delay that guarantees the new configuration information has spread all over the whole
network. The Forward Delay of a bridge depends on the diameter of the SWITCH network. Generally speaking,
the longer the network diameter is, the longer the forward delay should be set to be.
Run the following commands in global configuration mode.
Command Purpose
spanning-tree rstp forward-time
value Sets the Forward Delay.
no spanning-tree rstp forward-time
Resumes the default forward delay, 15
seconds.
It is especially noted that if Forward Delay is set too small the temporary redundant path may occur in the
network, but if Forward Delay is set too big the network may be disconnected for a long time. That's why users
are recommended to take the default value.
In the default settings, the forward delay of a bridge is 15 seconds.
35.2.4 Setting the Hello Time
A suitable hello time not only guarantees that a bridge can detect a link fault in a network promptly but also
occupies a few network resources.
Run the following commands in global configuration mode.
Command Purpose
spanning-tree rstp hello-time
value Sets the Hello Time.
no spanning-tree rstp hello-time
Resumes the hello time to the default value.
It takes attention that if a long hello time is set, packet loss in the links may cause a bridge not to receive the
hello packets for a long time and the bridge then regards the occurrence of link faults and starts spanning-tree
recalculation, but if a too short hello time is set the bridge will frequently send the configuration information and
then the network bandwidth will be heavily occupied and the network/CPU load will be increased. That's why
users are recommended to take the default value.
In the default settings, the hello time of a bridge is 2 seconds.
35.2.5 Setting the Max Age
The max age is used to judge whether the configuration information expires. Users can set the max age
according actual conditions.
Run the following commands in global configuration mode.
Command Purpose
spanning-tree rstp max-age
value Setting the Max Age
no spanning-tree rstp max-age
Resumes the max age to the default value, 20
seconds.
Link fault, reduces the network auto-adaptivity. We recommend user to use the default value. Note: if you