F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices Network Management Configuration Guide-6PW100

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count in BPDUs that it propagates. When the hop count of a BPDU reaches 0, it is discarded by the
device that received it. This prevents devices beyond the reach of the maximum hop from participating 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.
To configure the maximum number of hops of an MST region:
Ste
p
Command Remarks
134. Enter system view.
system-view N/A
135. Configure the maximum hops
of the MST region.
stp max-hops hops The default setting is 20.
431BConfiguring 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. Based on the network diameter you configured, the system automatically
sets an optimal hello time, forward delay, and max age for the device.
To configure the network diameter of a switched network:
Ste
p
Command Remarks
136. Enter system view.
system-view N/A
137. Configure the network diameter of the
switched network.
stp bridge-diameter diameter The default setting is 7.
In STP, RSTP, or 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.
432BConfiguring spanning tree timers
The following timers are used for spanning tree calculations:
• Forward delay—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. The port transitions its state after a forward delay timer
expires, to make sure the state transition of the local port remains 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 during every hello time interval. If the device receives no
configuration BPDUs within the hello time interval, it recalculates the spanning tree.
• Max age—In the CIST of an MSTP network, the device uses the max age parameter to determine
whether a configuration BPDU received by a port has expired. If it has, a new spanning tree
calculation process starts. The max age timer is ineffective for MSTIs.
To prevent network instability, make sure the timer settings meet the following formulas:
• 2 × (forward delay – 1 second) ≥ max age
• Max age ≥ 2 × (hello time + 1 second)