(Optional) Configuring an LDP Label Advertisement Mode

An LDP label advertisement mode can be configured to control LSP establishment.

Context

A downstream LSR sends a Label Mapping message to an upstream LSR in downstream unsolicited mode (DU) by default. This allows multiple LSPs including backup LSPs to be established. If a network fault occurs, services rapidly switch to a backup LSP, improving network reliability. Establishing a large number of LSPs burdens an LSR such as a digital subscriber link access multiplexer (DSLAM) that is a low-performance access device deployed on an MPLS network. On a large-scale network, a DSLAM can be configured to send Label Mapping messages to only upstream LSRs only after receiving requests for labels. This minimizes the number of unwanted MPLS forwarding entries forwarded by the DSLAM.

Procedure

Configuring an LDP Label Advertisement Mode of local LDP session.
1. Run system-view
  The system view is displayed.
2. Run interface interface-type interface-number
  The interface view is displayed.
3. Run mpls ldp advertisement { dod | du }
  A label advertisement mode is configured.
  A pair of LDP peers must have the same label advertisement mode. Inconsistency in label advertisement modes causes the two LDP peers to fail to establish LDP LSPs between them over multiple links.
  
  Modifying a configured label advertisement mode leads to the reestablishment of an LDP session, resulting in service interruptions.
4. Run commit
  The configuration is committed.
Configuring an LDP label advertisement mode of remote LDP session.
1. Run system-view
  The system view is displayed.
2. Run mpls ldp remote-peer remote-peer-name
  A remote MPLS LDP peer is created, and the remote MPLS LDP peer view is displayed.
3. Run mpls ldp advertisement { dod | du }
  A label advertisement mode is configured.
  
  When the local and remote LDP sessions coexist, they must have the same label advertisement mode.
4. Run commit
  The configuration is committed.