Enabling loop guard – H3C Technologies H3C WX6000 Series Access Controllers User Manual

Page 197

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To do...

Use the command...

Remarks

Enter system view

system-view

—

Enter Ethernet
interface view

interface interface-type
interface-number

Enter Ethernet
interface view
or port group
view

Enter port group
view

port-group

{ manual

port-group-name | aggregation

agg-id

}

Required
Use either command.
Configurations made in Ethernet
interface view will take effect on
the current port only;
configurations made in port group
view will take effect on all ports in
the port group.

Enable the root guard function on
the port(s)

stp root-protection

Required
Disabled by default

Enabling Loop Guard

By keeping receiving BPDUs from the upstream device, a device can maintain the state of the root port
and other blocked ports. However, due to link congestion or unidirectional link failures, these ports may
fail to receive BPDUs from the upstream device. In this case, the downstream device will reselect the
port roles: those ports failed to receive upstream BPDUs will become designated ports and the blocked
ports will transition to the forwarding state, resulting in loops in the switched network. The loop guard
function can suppress the occurrence of such loops.

If a loop guard–enabled port fails to receive BPDUs from the upstream device, and if the port took part
in STP calculation, all the instances on the port, no matter what roles they play, will be set to, and stay in,
the Discarding state.

It is recommended that you enable the loop guard feature on your device.

Follow these steps to enable loop guard: