label advertise

Function

The label advertise command configures the labels to be assigned to the penultimate hop.

The undo label advertise command restores the default label.

By default, the egress node assigns implicit-null labels to the penultimate hop.

Format

label advertise { explicit-null | implicit-null | non-null }

undo label advertise

Parameters

Parameter	Description	Value
explicit-null	Enables the egress node to assign explicit null labels to the penultimate hop if the penultimate hop does not support the PHP feature. If the information contained in the label needs to be sent to the penultimate hop, this parameter is required. The value of the explicit null label is 0(ipv4).	-
implicit-null	Enables the egress node to assign implicit null labels to the penultimate hop if the penultimate hop supports the PHP feature. The value of the implicit null label is 3.	-
non-null	Enables the egress node to assign common labels to the penultimate hop if the penultimate hop does not support the PHP feature. If the penultimate hop does not support the PHP feature, this parameter is required. The value of the label must be greater than or equal to 16.	-

Parameter

Description

Value

explicit-null

Enables the egress node to assign explicit null labels to the penultimate hop if the penultimate hop does not support the PHP feature. If the information contained in the label needs to be sent to the penultimate hop, this parameter is required. The value of the explicit null label is 0(ipv4).

implicit-null

Enables the egress node to assign implicit null labels to the penultimate hop if the penultimate hop supports the PHP feature. The value of the implicit null label is 3.

non-null

Enables the egress node to assign common labels to the penultimate hop if the penultimate hop does not support the PHP feature. If the penultimate hop does not support the PHP feature, this parameter is required. The value of the label must be greater than or equal to 16.

Views

MPLS view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
mpls-base	write

Usage Guidelines

Usage Scenario

Run the label advertise command to configure the type of labels assigned to the penultimate hop on the egress. The default configuration implicit-null is recommended. The setting eases the forwarding burden on the egress, improving the forwarding efficiency.

You can choose a type as needed.

implicit-null supports PHP, which allows the LSR at the penultimate hop to pop out the label from an MPLS packet and send the packet to the egress. After receiving the packet, the egress directly forwards the unlabeled IP packet or the single-labeled packet. PHP helps reduce the burden on the egress.
explicit-null does not support PHP. explicit-null supports MPLS QoS, which helps save label resources in the egress. If E2E services have QoS attributes carried in the EXP field in a label, explicit-null can be configured to save label resources and prevent EXP value loss.
non-null does not support PHP. The setting is resource consuming and is therefore not recommended. This parameter can be used when the egress needs to identify services based on labels.

Prerequisites

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

Precautions

The label advertise command takes effect on newly established LSPs. For existing LSPs, perform the one of following operations to make the command take effect:

On an LDP LSP, run the reset mpls ldp command in the user view on the local node.
On an SR-MPLS BE tunnel, run the reset isis all or reset isis process-id all command in the user view on the local node.

Example

# Configure the egress node to assign common null labels to the penultimate hop.

<HUAWEI> system-view
[~HUAWEI] mpls
[*HUAWEI-mpls] label advertise non-null