101
The change to the bridge ID of a device in the user access network might cause a change to the
spanning tree topology in the core network. To avoid this problem, you can enable port role
restriction on a port. With this feature enabled, when the port receives a superior BPDU, it becomes
an alternate port rather than a root port.
Make this configuration on the port that connects to the user access network.
To configure port role restriction:
Step
Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Layer 2 Ethernet or
aggregate interface view.
interface interface-type
interface-number
N/A
3.
Enable port role restriction.
stp role-restriction
By default, port role restriction is
disabled.
Configuring TC-BPDU transmission restriction
CAUTION:
Enabling TC-BPDU transmission restriction on a port might cause the previous forwarding address
table to fail to be updated when the topology changes.
The topology change to the user access network might cause the forwarding address changes to the
core network. When the user access network topology is unstable, the user access network might
affect the core network. To avoid this problem, you can enable TC-BPDU transmission restriction on
a port. With this feature enabled, when the port receives a TC-BPDU, it does not forward the
TC-BPDU to other ports.
Make this configuration on the port that connects to the user access network.
To configure TC-BPDU transmission restriction:
Step
Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Layer 2 Ethernet or
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 and be 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:
