auto-frr lsp-trigger

Function

The auto-frr lsp-trigger command configures a policy for triggering LDP to establish backup LSPs based on backup routes.

The undo auto-frr lsp-trigger command restores the default setting.

By default, LDP uses backup routes with 32-bit addresses to establish backup LSPs.

Format

auto-frr lsp-trigger { all | host | ip-prefix ip-prefix-name | none }

undo auto-frr lsp-trigger

Parameters

Parameter	Description	Value
all	Specifies all backup routes to trigger LDP to establish backup LSPs.	-
host	Specifies backup routes with 32-bit addresses to trigger LDP to establish backup LSPs.	-
ip-prefix ip-prefix-name	Specifies IP prefix list to trigger LDP to establish backup LSPs.	The value is an existing IP prefix list name.
none	Specifies no backup routes to trigger LDP to establish backup LSPs.	-

Views

MPLS-LDP view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

On an MPLS network with a backup link, if a link fault occurs, Interior Gateway Protocol (IGP) routes converge and routes related to the backup link become available. After IGP route convergence is complete, an LDP LSP over the backup link becomes available. During this process, traffic is interrupted. To prevent traffic interruption, you can configure LDP fast reroute (FRR). On the network enabled with LDP FRR, if an interface failure (detected by the interface itself or by an associated BFD session) or a primary LSP failure (detected by an associated BFD session) occurs, LDP FRR is notified of the failure and rapidly forwards traffic to a backup LSP, protecting traffic on the primary LSP. The traffic switchover is performed within 50 milliseconds, avoiding traffic interruption.

LDP FRR is classified into the following types:

LDP manual FRR: A backup LSP is configured manually by specifying an outbound interface or a next hop. The configuration is complex but flexible because a backup LSP can be configured manually. LDP manual FRR applies to simple networks.
Auto LDP FRR: A backup LSP is automatically created based on a specified policy. The configuration is simple and loop-free. Auto LDP FRR applies to complex and large networks.

Auto LDP FRR depends on the automatic reroute function of IGP. Auto LDP FRR is automatically enabled after IGP automatic reroute is enabled using the frr (IS-IS) command. To change the policy for triggering LDP to establish backup LSPs, run the auto-frr lsp-trigger command.

Prerequisites

MPLS LDP has been enabled globally using the mpls ldp(system view) command in the system view.

Precautions

During LDP GR, changing the policy for triggering the setup of backup LSPs is not allowed.

If both the auto-frr lsp-trigger command and the lsp-trigger command are run, the established backup LSPs are controlled by both the policy for triggering LDP LSP establishment and the policy for triggering backup LDP LSP establishment. For example, if the policy for triggering LDP LSP establishment is none and that for triggering backup LDP LSP establishment is all, the backup LDP LSP is established using the none policy.

Creating an IP prefix list before it is referenced is recommended. By default, nonexistent IP prefix lists cannot be referenced using the command. If the route-policy nonexistent-config-check disable command is run in the system view and a nonexistent IP prefix list is referenced using the current command, all backup routes trigger backup LDP LSP establishment.

Example

#Configure the policy for specifying no backup routes to trigger LDP to establish backup LSPs.

<HUAWEI> system-view
[HUAWEI] mpls ldp
[HUAWEI-mpls-ldp] auto-frr lsp-trigger none