H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 102)

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Configure BPDU guard on a device with edge ports configured. BPDU guard does not take effect on
loopback testing-enabled ports. For more information about loopback testing, see "Configuring Ethernet
interfaces."
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, because of possible configuration errors or malicious attacks on
the network, the legal root bridge might receive a configuration BPDU with a higher priority. Another
device will supersede the current legal root bridge, causing an undesired change in 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 the root guard function 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 immediately sets that port to the listening state
in the MSTI, without forwarding the packet. This is equivalent to disconnecting the link connected with
this port in the MSTI. If the port receives no BPDUs with a higher priority after a period that is twice the
forwarding delay, it reverts to its original state.
Configure root guard on a designated port. You cannot configure root guard and loop guard on a port
at the same time.
To enable root guard:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view or port
group view.
• Enter Layer 2 Ethernet interface view or
Layer 2 aggregate interface view:
interface interface-type interface-number
• Enter port group view:
port-group manual port-group-name
Use one of the commands.
3. Enable the root guard
function for the ports.
stp root-protection
By default, root guard is
disabled.
Enabling loop guard
By continuing to receive BPDUs from the upstream device, a device can maintain the state of the root port
and blocked ports. However, link congestion or unidirectional link failures might cause these ports to fail
to receive BPDUs from upstream devices. The device will reselect the port roles: Those ports in forwarding
state that failed to receive upstream BPDUs will become designated ports, and the blocked ports will