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Item Description
Timers
Set the timers:
• Forward Delay—Set the delay for the root and designated ports to
transit to the forwarding state. The length of the forward delay time is
related to the network diameter of the switched network. The larger the
network diameter is, the longer the forward delay time should be. If the
forward delay setting is too small, temporary redundant paths might be
introduced. If the forward delay setting is too big, it might take a long
time for the network to converge. Hewlett Packard Enterprise
recommends that you use the default setting.
• Hello Time—Set the interval at which the device sends hello packets to
the surrounding devices to make sure the paths are fault-free. A correct
hello time setting enables the device to timely detect link failures on the
network without using excessive network resources. If the hello time is
set too long, the device will take packet loss as a link failure and trigger
a new spanning tree calculation process. If the hello time is set too
short, the device will send repeated configuration BPDUs frequently.
This adds to the device burden and wastes network resources. Hewlett
Packard Enterprise recommends that you use the default setting.
• Max Age—Set the maximum length of time a configuration BPDU can
be held by the device. If the max age time setting is too small, the
network devices will frequently launch spanning tree calculations and
might take network congestion as a link failure. If the max age setting is
too large, the network might fail to timely detect link failures and fail to
timely launch spanning tree calculations, reducing the auto-sensing
capability of the network. Hewlett Packard Enterprise recommends that
you use the default setting.
When you configure timers, follow these guidelines:
• The settings of hello time, forward delay and max age must meet a
certain formula. Otherwise, the network topology will not be stable.
Hewlett Packard Enterprise recommends you to set the network
diameter, and then have the device automatically calculate the forward
delay, hello time, and max age.
• The bridge diameter cannot be configured together with the timers.
Instance
• Instance ID—Set the ID of the MSTI to be configured.
• Root Type—Set the role of the device in the MSTI:
Not Set—The device role is not configured.
Primary—Configure the device as the root bridge.
Secondary—Configure the device as a secondary root bridge.
• Bridge Priority—Set the bridge priority of the device, which is one of
the factors determining whether the device can be elected as the root
bridge.
After specifying the current device as the primary root bridge or a secondary
root bridge, you cannot change the priority of the device.
TC Protection
Select whether to enable TC-BPDU guard.
When receiving topology change (TC) BPDUs, the device flushes its
forwarding address entries. If someone forges TC-BPDUs to attack the
device, the device will receive a large number of TC-BPDUs within a short
time and frequently flushes its forwarding address entries. This affects
network stability.
The TC-BPDU guard function prevents frequent flushing of forwarding
address entries.
Hewlett Packard Enterprise recommends not disabling this function.
TC Protection
Threshold
Set the maximum number of immediate forwarding address entry flushes the
device can perform within a certain period of time after receiving the first
TC-BPDU.
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