H3C Technologies H3C S10500 Series Switches - Manual (Page 92)

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device that received it. This prevents devices beyond the reach of the maximum hop from participate in
spanning tree calculation, so the size of the MST region is limited.
Make this configuration on the root bridge only. All other devices in the MST region use the maximum
hop value set for the root bridge.
Follow these steps to configure the maximum number of hops of an MST region:
To do... Use the command... Remarks
Enter system view system-view —
Configure the maximum hops of
the MST region
stp max-hops hops
Required
20 by default.
Configuring the network diameter of a switched network
Any two terminal devices in a switched network are connected 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.
Follow these steps to configure the network diameter of a switched network:
To do... Use the command... Remarks
Enter system view system-view —
Configure the network diameter of the switched
network (in STP/RSTP/MSTP mode)
stp bridge-diameter diameter
Configure the network diameter of the switched
network (in PVST mode) stp vlan vlan-list
bridge-diameter diameter
Required
Use either command.
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.
• In STP/RSTP/MSTP mode, 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.
• In PVST mode, the network diameter configuration is effective on the root bridge only.
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 ensure that
the state transition of the local port keeps synchronized with the peer.
• Hello time
The device detects whether a link failure has occurred with the hello time interval. The spanning tree
sends a configuration BPDU every hello time interval. If the device receives no configuration BPDUs
within the hello time interval, it recalculates the spanning tree.