mpls poison-reverse enable

Function

The mpls poison-reverse enable command enables MPLS poison reverse.

The undo mpls poison-reverse enable command disables MPLS poison reverse.

By default, this function is disabled.

Format

mpls poison-reverse enable

undo mpls poison-reverse enable

Parameters

None

Views

100GE interface view, 400GE interface view, 40GE interface view, Eth-Trunk sub-interface view, Eth-Trunk interface view, GE sub-interface view, GE interface view, XGE interface view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
forwarding	write

Usage Guidelines

Usage Scenario

On an LDP/SR-MPLS BE ring network with FRR/TILFA configured, if the primary LDP LSP fails, the ingress switches traffic from the primary LSP to the backup LSP. If routes are not converged before the LSP switchover is complete, the transit node sends traffic back to the ingress. As a result, a loop occurs. To resolve this issue, run the mpls poison-reverse enable command to enable LDP FRR/ECMP poison reverse on the traffic inbound interface of the transit node. With this function enabled, the transit node rapidly switches traffic to the backup LSP after learning that the outbound interface is the same as the inbound interface.

This command also applies to an LDP/SR-MPLS BE ring network with two ECMP paths configured.

Precautions

For Eth-Trunk sub-interface and GE sub-interface views, this command is supported only by Eth-Trunk and GE sub-interfaces for dot1q VLAN tag termination.

This command takes effect on Layer 3 interfaces, not Layer 2 interfaces.

Do not configure the LDP poison reverse function on nodes where traffic may be sent and received by the same interface, which helps prevent a device from incorrectly determining that a loop occurs. The node can be the egress of a protection LDP LSP, such as an LDP FRR LSP, LDP RLFA LSP, or backup LDP LSP in LDP over TE.

Example

# On GE 0/1/16, enable MPLS poison reverse.

<HUAWEI> system-view
[~HUAWEI] interface GigabitEthernet0/1/16
[*HUAWEI-GigabitEthernet0/1/16] mpls poison-reverse enable