Configuring the TTL and EXP Processing Mode When the Explicit Null Label Is Used

This section describes how to configure the TTL and EXP processing mode when the explicit null label is used.

Background

If the explicit null label and the uniform mode are configured, an egress PE copies the TTL and EXP values to the IP or inner packets before forwarding them out of a public network. If the explicit null label and the pipe mode are configured, an egress PE does not copy the TTL or EXP values to the IP or inner packets.

In VS mode, this configuration task is supported only by the admin VS.

Prerequisites

Completing the following tasks:

Configure the MPLS functions.
Configure the egress PE to assign the explicit null label upstream.

Precautions

The configuration takes effect only on the egress PE.

Procedure

Run system-view
The system view is displayed.
Run mpls
The MPLS view is displayed.
Run label advertise explicit-null
The egress PE is enabled to assign the explicit null label upstream.
Run explicit-null-label ttl-mode { uniform | pipe }
The mode used by the egress PE to process TTL values is configured.

Either of the following modes can be used:
- uniform: The egress PE copies the TTL value in an MPLS packet to the TTL field in the IP or inner packet.
- pipe: The egress PE does not copy the TTL value in an MPLS packet to the TTL field in the IP or inner packet.
Run explicit-null-label exp-mode { uniform | pipe }
The mode used by the egress PE to process EXP values is configured.

Either of the following modes can be used:
- 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.
Run commit
The configuration is committed.