(Optional) Configuring a Policy for Triggering LDP LSP Establishment

Context

After MPLS LDP is enabled, LSPs are automatically established. If no policy is configured, an increasing number of LSPs are established, wasting resources.

Configure the lsp-trigger command on the ingress and egress nodes to trigger LSP establishment based on routes matching specified conditions. This setting controls the number of LSPs and saves network resources.
Configure the propagate mapping command on the transit node to trigger LSP establishment based on routes matching specified conditions. For the routes that do not match specified conditions, the local device does not send Label Mapping messages to the upstream device, which reduces the number of LSPs and saves network resources.

By default, the lsp-trigger command is recommended. If this command cannot be configured on the ingress and egress nodes, configure the propagate mapping command on the transit node.

Procedure

Perform the following steps on the ingress and egress nodes:
1. Run system-view
  The system view is displayed.
2. Run mpls
  The MPLS view is displayed.
3. Use either the following commands to configure a policy for triggering LSP establishment.
  - Run lsp-trigger { all | host | ip-prefix ip-prefix-name | none }
    
    A policy for triggering LSP establishment based on static and IGP routes is configured.
    
    By default, the policy is host. This policy allows LDP to use 32-bit host routes (except 32-bit host routes of interfaces) to establish LSPs.
    
    LSPs can be established using exactly matching routes on LSRs. On a loopback interface with 32-bit mask, an LSP can be established only when an exactly matching host route is available.
  - Run lsp-trigger bgp-label-route [ ip-prefix ip-prefix-name ] [ not-only-host ]
    
    A policy for triggering LSP establishment based on labeled public BGP routes is configured.
    
    By default, LDP does not distribute labels to labeled public BGP routes.
4. Run proxy-egress disable
  The device is disabled from establishing proxy egress LSPs.
  
  By default, a device is enabled to establish proxy egress LSPs.
  
  If a policy allows a device to use all static and IGP routes to establish LSPs or use an IP address prefix list to establish LSPs, the policy also triggers proxy egress LSP establishment. However, the proxy egress LSPs may be unnecessary, wasting system resources. To prevent this problem, run the proxy-egress disable command to disable a device from establishing such proxy egress LSPs.
Perform the following steps on the transit node:
1. Run system-view
  The system view is displayed.
2. Run mpls ldp
  The MPLS LDP view is displayed.
3. Run propagate mapping for ip-prefix ip-prefix-name
  LDP is configured to establish LSPs based on routes filtered out based on the IP address prefix list.
  
  By default, when LDP establishes an LSP, LDP does not filter out received routes.