R0106-HP MSR Router Series Layer 2 - LAN Switching Configuration Guide(V7)

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Step Command Remarks
1. Enter system view.
system-view N/A
2. Enter Layer 2 Ethernet
interface view.
interface interface-type interface-number N/A
3. Enable the root guard
function.
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 the upstream devices. In this situation, the device reselects the port roles:
• Those ports in forwarding state that failed to receive upstream BPDUs become designated ports.
• The blocked ports transit to the forwarding state.
As a result, loops occur 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,
it transits its state. Otherwise, it stays in the discarding state to prevent temporary loops.
Do not enable loop guard on a port that connects user terminals. Otherwise, the port stays in the
discarding state in all MSTIs because it cannot receive BPDUs.
On a port, the loop guard function is mutually exclusive with the root guard function or the edge port
setting.
Configure loop guard on the root port and alternate ports of a device.
To enable loop guard:
Step Command Remarks
1. Enter system view.
system-view N/A
2. Enter Layer 2 Ethernet
interface view.
interface interface-type interface-number N/A
3. Enable the loop guard
function for the ports.
stp loop-protection
By default, loop guard is
disabled.
Configuring port role restriction
CAUTION:
Use this feature with caution, because enablin
g
port role restriction on a port mi
g
ht affect the connectivity
of the spanning tree topology.
The bridge ID change 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.