H3C Technologies H3C S5120 Series Switches - Manual (Page 187)

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z
2 × (forward delay – 1 second) ƒ max age
z
Max age ƒ 2 × (hello time + 1 second)
We recommend that you specify the network diameter with the stp bridge-diameter command and let
MSTP automatically calculate optimal settings of these three timers based on the network diameter.
Configuring the Timeout Factor
The timeout factor is a parameter used to decide the timeout time, as shown in the following formula:
Timeout time = timeout factor × 3 × hello time.
After the network topology is stabilized, each non-root-bridge device forwards configuration BPDUs to
the downstream devices at the interval of hello time to check whether any link is faulty. Typically, if a
device does not receive a BPDU from the upstream device within nine times the hello time, it assumes
that the upstream device has failed and starts a new spanning tree calculation process.
Sometimes a device may fail to receive a BPDU from the upstream device because the upstream
device is busy. A spanning tree calculation that occurs in this case not only is unnecessary, but also
wastes the network resources. In a very stable network, you can avoid such unwanted spanning tree
calculations by setting the timeout factor to 5, 6, or 7.
Follow these steps to configure the timeout factor:
To do... Use the command... Remarks
Enter system view system-view —
Configure the timeout factor of the
device
stp timer-factor factor
Required
3 by default
Configuring the Maximum Port Rate
The maximum rate of a port refers to the maximum number of BPDUs the port can send within each
hello time. The maximum rate of a port is related to the physical status of the port and the network
structure.
Make this configuration on the root bridge and on the leaf nodes separately.
Follow these steps to configure the maximum rate of a port or a group of ports:
To do... Use the command... Remarks
Enter system view system-view —
Enter Layer 2
Ethernet port view, or
Layer 2 aggregate
port view
interface interface-type
interface-number
Enter port
view or port
group view
Enter port group view
port-group manual
port-group-name
Required
Use either command.
Configure the maximum rate of the
ports
stp transmit-limit limit
Required
10 by default