(Optional) Configuring a Policy for Triggering LDP LSP Establishment

A policy can be configured to allow LDP to establish LSPs based on eligible routes.

Context

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

A policy can be configured to allow LDP to use eligible routes to establish ingress and egress LSPs on a public network. The policy allows only specified routes to trigger LDP LSP establishment, controlling the number of LSPs and minimizing resource wastes.

Do not use the lsp-trigger all command. If this command is run, all static and IGP routes can be used by LDP to establish LSPs. This causes a large number of unwanted LSPs to be established, wasting system resources. Before using the lsp-trigger all command, configure a policy for filtering out routes that LDP will not use to establish LSPs. This reduces the number of LSPs to be established and saves system resources.

Procedure

Access the system view.
```
system-view
```
Access the MPLS view.
```
mpls
```
Perform either of the following steps to configure a policy for triggering LDP LSP establishment:
- Allow static routes and IGP routes to trigger LDP LSP establishment:
```
lsp-trigger { all | host | ip-prefix ip-prefix-name | none }
```
- Allow labeled public network BGP routes to trigger LDP LSP establishment:
```
lsp-trigger bgp-label-route [ ip-prefix ip-prefix-name ]
```
One of the following parameters can be configured for a trigger policy:
- host: is the default policy and allows LDP to use 32-bit host-address route (except 32-bit host-address of interfaces) to establish LSPs.
- all: allows LDP to use all static and IGP routes, but not public network BGP routes, to establish LSPs.
- ip-prefix: allows LDP to use the routes that match an IP address prefix list to establish LSPs.
- none: does not allow LDP to use any routes to establish LSPs.
- bgp-label-route: allows LDP to use labeled public network BGP routes to establish LSPs.
LSPs can be established using exactly matching routes on LSRs. For example, an exactly matching host route to an IP address with a 32-bit mask of a loopback interface can be used to trigger LSP establishment.

A policy for triggering LSP establishment cannot be modified during the LDP graceful restart (GR) process.
Configure a policy for disabling a device from establishing proxy egress LSPs.
```
proxy-egress disable
```
If the current policy allows a device to establish LSPs for all static and IGP routes 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 unavailable, which wastes system resources. To prevent this problem, run the proxy-egress disable command to disable a device from establishing such proxy egress LSPs.

During the LDP GR, the proxy-egress disable command cannot be run.