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Configure Bridge’s Routing Function 301
Table 330 Configure the interval for sending BPDUs
By default, the value of Hello Time timer is 2 seconds. It is in the range of 1 to
10 seconds.
When configuring the Hello Time timer, it should be noted that:
■ In the spanning tree, all the bridges use the time value of Hello Time timer
of the root bridge, and their own configurations take no effect.
■ Too long a Hello Time will cause the bridge to recompute the spanning tree
because it considers the packet dropping of the link as link fault, whereas
too short a Hello Time will cause it to send BPDUs frequently and thus
exacerbate the bridge CPU load. It is recommended that users use the
default value.
f Configure the forward delay for the port status transition
Link faults may cause the network to recompute the spanning tree topology.
However, the recomputed new BPDU cannot be propagated throughout the
network right away. If the newly elected root port and the designated port
begin to forward data immediately, a temporary loop may be incurred. In STP, a
transitional state mechanism is thus adopted. Specifically, the root port and the
designated ports will undergo a transitional state for an interval of forward
delay to enter the forwarding state to resume the data forwarding. Such a
delay ensures that the new BPDU has already been propagated throughout the
network before the data frames are forwarded according to the latest
topology. The forward delay timer is thus used to control the interval for the
system waiting to enter the Forwarding state.
Perform the following configuration in system view.
Table 331 Configure the forward delay for the port status transition
By default, the value of the forward delay timer is 15 seconds. It is in the range
of 4 to 200 seconds.
When configuring the forward delay timer, note that:
■ No matter what its individual configuration might be, all the bridges in the
spanning tree should use the time value of the forward delay timer of the
root bridge.
■ If the forward delay is configured too short, temporary redundant paths
may be introduced. If the forward delay is configured too long, however,
the restoring of network connection may take a long time because the STP
cannot converge to a stable state for a long period. It is recommended that
users use the default value.
g Configure the Max Age of BPDU
Operation Command
Configure Hello Time timer bridge stp timer hello seconds
Restore the default value of the Hello Time timer undo bridge stp timer hello
Operation Command
Configure the forward delay timer bridge stp timer
forward-delay
seconds
Restore the default value of the forward delay timer undo bridge stp timer
forward-delay