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Step Command
Remarks
2.
Enter Layer 2 Ethernet
interface or Layer 2
aggregate interface view.
interface interface-type
interface-number
N/A
3.
Enable TC-BPDU
transmission restriction.
stp tc-restriction
By default, TC-BPDU
transmission restriction is
disabled.
Enabling TC-BPDU guard
When a device receives topology change (TC) BPDUs (the BPDUs that notify devices of topology
changes), it flushes its forwarding address entries. If someone uses TC-BPDUs to attack the device,
the device will receive a large number of TC-BPDUs within a short time. Then, the device is busy with
forwarding address entry flushing. This affects network stability.
TC-BPDU guard allows you to set the maximum number of immediate forwarding address entry
flushes performed within 10 seconds after the device receives the first TC-BPDU. For TC-BPDUs
received in excess of the limit, the device performs a forwarding address entry flush when the time
period expires. This prevents frequent flushing of forwarding address entries. As a best practice,
enable TC-BPDU guard.
To enable TC-BPDU guard:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enable the TC-BPDU guard feature.
stp tc-protection
By default, TC-BPDU guard
is enabled.
As a best practice, do not
disable this feature.
3.
(Optional.) Configure the maximum
number of forwarding address entry
flushes that the device can perform
every 10 seconds.
stp tc-protection threshold
number
The default setting is 6.
Enabling BPDU drop
In a spanning tree network, every BPDU arriving at the device triggers an STP calculation process
and is then forwarded to other devices in the network. Malicious attackers might use the vulnerability
to attack the network by forging BPDUs. By continuously sending forged BPDUs, they can make all
devices in the network continue performing STP calculations. As a result, problems such as CPU
overload and BPDU protocol status errors occur.
To avoid this problem, you can enable BPDU drop on ports. A BPDU drop-enabled port does not
receive any BPDUs and is invulnerable to forged BPDU attacks.
To enable BPDU drop on an Ethernet interface:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Layer 2 Ethernet
interface view.
interface interface-type
interface-number
N/A
3.
Enable BPDU drop on the
interface.
bpdu-drop any
By default, BPDU drop is
disabled.
