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Step
1.
Enter system view.
2.
Enter interface view or port group
view.
3.
Enable the root guard function for
the port(s).
NOTE:
Among loop guard, root guard and edge port settings, only one function (whichever is configured the
earliest) can take effect on a port at the same time.
Enabling loop guard
By keeping receiving BPDUs from the upstream device, a router can maintain the state of the root port
and blocked ports. However, due to link congestion or unidirectional link failures, these ports may fail to
receive BPDUs from the upstream devices. The router 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
transition to the forwarding state, resulting in loops in the switched network. The loop guard function can
suppress the occurrence of such loops.
The initial state of a loop guard-enabled port is discarding in every MSTI. When the port receives BPDUs,
its state transitions normally. Otherwise, it stays in the discarding state to prevent temporary loops.
Make this configuration on the root port and alternate ports of a router.
To enable loop guard:
Step
1.
Enter system view.
2.
Enter interface view or port group
view.
3.
Enable the loop guard function for
the ports.
Command
system-view
•
Enter Ethernet interface view or
Layer 2 aggregate interface
view:
interface interface-type
interface-number
•
Enter port group view:
port-group manual
port-group-name
stp root-protection
Command
system-view
•
Enter Ethernet interface view or
Layer 2 aggregate interface
view:
interface interface-type
interface-number
•
Enter port group view:
port-group manual
port-group-name
stp loop-protection
61
Remarks
N/A
Use either command.
By default, root guard is
disabled.
Remarks
N/A
Use either command.
By default, loop guard is
disabled.
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