H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 79)

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The regional root bridge always sends a configuration BPDU with a hop count set to the maximum value.
When a device receives this configuration BPDU, it decrements the hop count by 1 and uses the new hop
count in the BPDUs it propagates. When the hop count of a BPDU reaches 0, it is discarded by the device
that received it. Devices beyond the reach of the maximum hop can no longer take part in spanning tree
calculation, and the size of the MST region is confined.
Make this configuration on the root bridge only. All the devices other than the root bridge in the MST
region use the maximum hop value set for the root bridge.
To configure the maximum number of hops of an MST region:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure the maximum hops
of the MST region.
stp max-hops hops 20 by default.
Configuring the network diameter of a switched
network
Any two terminal devices in a switched network are interconnected through a specific path composed of
a series of devices. The network diameter is the number of devices on the path composed of the most
devices. The network diameter is a parameter that indicates the network size. A bigger network diameter
indicates a larger network size.
To configure the network diameter of a switched network:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure the network diameter of
the switched network.
stp bridge-diameter diameter 7 by default.
NOTE:
•
Based on the network diameter you configured, the system automatically sets an optimal hello time,
forward delay, and max age for the device.
• Each MST region is considered as a device and the configured network diameter is effective only for the
CIST (or the common root bridge), but not for MSTIs.
Configuring spanning tree timers
The following timers are used for spanning tree calculation:
• Forward delay
It is the delay time for port state transition. To prevent temporary loops on a network, the spanning
tree sets an intermediate port state, the learning state, before it transitions from the discarding state
to the forwarding state, and requires that the port transitions its state after a forward delay timer to
make sure that the state transition of the local port keeps synchronized with the peer.
• Hello time