99
•
BPDU guard
•
Root guard
•
Loop guard
•
Port role restriction
•
TC-BPDU transmission restriction
•
TC-BPDU guard
•
BPDU drop
Enabling BPDU guard
For access layer devices, the access ports can directly connect to the user terminals (such as PCs)
or file servers. The access ports are configured as edge ports to allow rapid transition. When these
ports receive configuration BPDUs, the system automatically sets the ports as non-edge ports and
starts a new spanning tree calculation process. This causes a change of network topology. Under
normal conditions, these ports should not receive configuration BPDUs. However, if someone uses
configuration BPDUs maliciously to attack the devices, the network will become unstable.
The spanning tree protocol provides the BPDU guard function to protect the system against such
attacks. When edge ports receive configuration BPDUs on a device with BPDU guard enabled, the
device performs the following tasks:
•
Shuts down these ports.
•
Notifies the NMS that these ports have been shut down by the spanning tree protocol.
The device reactivates the shutdown ports after a detection interval. For more information about this
detection interval, see
Fundamentals Configuration Guide
.
BPDU guard does not take effect on loopback-testing-enabled ports. For more information about
loopback testing, see "
Configuring Ethernet interfaces
."
Configure BPDU guard on a device with edge ports configured.
To enable BPDU guard:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enable the BPDU guard
function for the device.
stp bpdu-protection
By default, BPDU guard is
disabled.
Enabling root guard
The root bridge and secondary root bridge of a spanning tree should be located in the same MST
region. Especially for the CIST, the root bridge and secondary root bridge are put in a high-bandwidth
core region during network design. However, due to possible configuration errors or malicious
attacks in the network, the legal root bridge might receive a configuration BPDU with a higher priority.
Another device supersedes the current legal root bridge, causing an undesired change of the
network topology. The traffic that should go over high-speed links is switched to low-speed links,
resulting in network congestion.
To prevent this situation, MSTP provides the root guard function. If root guard is enabled on a port of
a root bridge, this port plays the role of designated port on all MSTIs. After this port receives a
configuration BPDU with a higher priority from an MSTI, it performs the following tasks:
•
Immediately sets that port to the listening state in the MSTI.
•
Does not forward the received configuration BPDU.
