explicit-null-label

Function

The explicit-null-label ttl-mode command configures a mode used by an egress PE to process the TTL field in packets when the explicit null label is assigned to a penultimate node.

The explicit-null-label exp-mode command configures a mode used by an egress PE to process the EXP field in packets when the explicit null label is assigned to a penultimate node.

By default, the processing mode is uniform mode.

Format

explicit-null-label exp-mode { uniform | pipe }

explicit-null-label ttl-mode { uniform | pipe }

Parameters

Parameter	Description	Value
uniform	Specifies uniform mode.	-
pipe	Specifies pipe mode.	-

Parameter

Description

Value

uniform

Specifies uniform mode.

pipe

Specifies pipe mode.

Views

MPLS view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
config	write

Usage Guidelines

Usage Scenario

If an explicit null label is used, a device processes the TTL field in MPLS packets in either of the following modes:

uniform: The egress reduces the MPLS TTL by one, compares the MPLS TTL with the IP TTL, and obtains the smaller value to map it to the IP TTL.
pipe: The egress reduces the IP TTL by one, without propagating the MPLS TTL to the IP TTL.
If an explicit null label is used, an egress PE processes the EXP field in MPLS packets in either of the following modes:
uniform: The egress PE copies the EXP value in an MPLS packet to the EXP field in the IP or inner packet.
pipe: The egress PE does not copy the EXP value in an MPLS packet to the EXP field in the IP or inner packet.

Prerequisites

MPLS has been enabled globally using the mpls command in the system view. The egress PE has been enabled to advertise the explicit null label using the label advertise explicit-null command.

Implementation Procedure

After the command line is configured, it takes effect immediately.

Precautions

This command takes effect only on the egress PE.

Example

# Enable a device to process the EXP field in pipe mode when assigning the explicit null label upstream.

<HUAWEI> system-view
[~HUAWEI] mpls
[~HUAWEI-mpls] explicit-null-label exp-mode pipe

# Enable a device to process the EXP field in uniform mode when assigning the explicit null label upstream.

<HUAWEI> system-view
[~HUAWEI] mpls
[~HUAWEI-mpls] explicit-null-label exp-mode uniform

# Enable a device to process the TTL field in pipe mode when assigning the explicit null label upstream.

<HUAWEI> system-view
[~HUAWEI] mpls
[~HUAWEI-mpls] explicit-null-label ttl-mode pipe

# Enable a device to process the TTL field in uniform mode when assigning the explicit null label upstream.

<HUAWEI> system-view
[~HUAWEI] mpls
[~HUAWEI-mpls] explicit-null-label ttl-mode uniform