loop-detect enable

Function

The loop-detect enable command enables L2VPN loop detection on an interface.

The undo loop-detect enable command disables L2VPN loop detection on the interface.

By default, L2VPN loop detection is disabled on the interface.

Format

loop-detect enable

undo loop-detect enable

Parameters

None

Views

Interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

Redundant links are used on an Ethernet switching network to provide link backup and enhance network reliability. The use of redundant links, however, may produce loops, causing broadcast storms and unstable MAC address entries. This degrades communication quality or even interrupts communication. On a traditional Layer 2 network, the Spanning Tree Protocol (STP) is usually used to prevent loops.

VPLS is an L2VPN technology providing LAN-like services over the MPLS network. It allows sites in diverse locations to connect the MPLS network and communicate with each other, which frees Ethernet LAN deployment from restrictions imposed by physical locations. As a Layer 2 Ethernet technology, VPLS has the following disadvantages:

If the customer network leases multiple lines, loops may occur due to incorrect customer configuration or in other unexpected cases, leading to broadcast storms.
If the customer network traverses a third-party network, loops may occur due to incorrect third-party network configuration or in other unexpected cases, leading to broadcast storms.

STP needs to be deployed on CEs, having high dependency on the customer network. The complex and changing features of the customer network increase the maintenance difficulty of the carrier.

To prevent loops on an L2VPN network, you can run the loop-detect enable command on an AC interface of a PE to configure L2VPN loop detection on the AC interface. After this function is enabled, when detecting a loop on the L2VPN network, the PE will automatically block an interface on the loop, report an alarm, and eliminate the loop.

Prerequisites

The interface has been bound to a VSI instance using the l2 binding command on the interface.

The interface must be an AC interface bound to a specified VSI. For details about the binding between an AC interface and a VSI, see Binding VSIs to AC Interfaces.
VSI encapsulation must use the VLAN encapsulation format that meets the 802.1Q standard. For details about how to configure the VSI encapsulation mode, see encapsulation (VSI view).

Example

# Enable L2VPN loop detection on GigabitEthernet0/0/1.

<HUAWEI> system-view
[HUAWEI] interface gigabitethernet 0/0/1
[HUAWEI-GigabitEthernet0/0/1] undo portswitch
[HUAWEI-GigabitEthernet0/0/1] l2 binding vsi company2
[HUAWEI-GigabitEthernet0/0/1] loop-detect enable