The outbound peer split-horizon command enables split horizon on a label switching router (LSR) to allow the LSR to distribute labels only to its upstream LDP peers.
The undo outbound peer split-horizon command restores the default configuration.
By default, split horizon is not enabled, which means that an LSR distributes labels to both upstream and downstream LDP peers.
outbound peer { peer-id | all } split-horizon
undo outbound peer { peer-id | all } [ split-horizon ]
| Parameter | Description | Value |
|---|---|---|
| peer-id | Specifies the LSR ID of an LDP peer. | - |
| all | Indicates all LDP peers. | - |
| split-horizon | Allocates labels only to the upstream LDP peer. | - |
Usage Scenario
An LSR sends Label Mapping messages to both upstream and downstream LDP peers by default, speeding up LDP label switched path (LSP) convergence. This leads to a great number of unwanted LSPs to be established, wasting resources. To reduce the number of LSPs and saving memory resources, run the outbound peer { peer-id | all } split-horizon command to configure an LDP split horizon policy, enabling the LSR to send Label Mapping messages only to upstream LDP peers.
peer-id: prevents the LSR from distributing labels to a specified downstream peer.
all: prevents the LSR from distributing labels to all downstream peers.
Prerequisites
MPLS LDP has been enabled globally using the mpls ldp command in the system view.
Configuration Impact
The LSR does not distribute labels to specified downstream peers.
Precautions
The all parameter takes preference over the peer-id parameter. For example, the outbound peer all split-horizon and then outbound peer 2.2.2.2 split-horizon commands are run, the outbound peer all split-horizon command can be saved in the configuration file and take effect, not the outbound peer 2.2.2.2 split-horizon command.