4000 Router Series MPLS Configuration Guide

277

Configuring MPLS OAM

Overview

MPLS Operation, Administration and Maintenance (OAM) provides fault management tools for MPLS

data plane connectivity verification, data plane and control plane consistency verification, and fault

locating. These fault management tools include the following types:

• On-demand tools—Tools that need to be triggered manually, such as MPLS ping and MPLS

traceroute.

• Proactive tools—Tools that are triggered by the system automatically, such as periodic MPLS

traceroute, and MPLS BFD.

You can use these tools to detect and locate faults of LSPs and MPLS TE tunnels.

MPLS ping

MPLS ping tests the connectivity of an LSP tunnel. At the ingress node, MPLS ping adds the label

associated with a tunnel into an MPLS echo request and sends it to the egress node over the tunnel. The

egress node processes the request and returns an MPLS echo reply to the ingress node. An MPLS echo

reply with a success notification indicates that the tunnel is available for data forwarding, and an MPLS

echo reply with an error code indicates that the tunnel has failed.

MPLS traceroute

MPLS traceroute displays the path that an MPLS LSP tunnel travels from the ingress node to the egress

node to locate errors on the tunnel. MPLS traceroute consecutively sends MPLS echo requests along the

LSP tunnel, with the TTL increasing from 1 to a specific value. Each hop along the tunnel returns an MPLS

echo reply to the ingress due to TTL timeout so the ingress can collect information about each hop along

the tunnel. This information allows you to locate the failed node or access information for each hop, for

example, the label allocated by each downstream hop.

Periodic MPLS traceroute

The periodic MPLS traceroute function automatically traces an LSP tunnel at a specific interval. It locates

errors on the LSP tunnel, verifies the consistency of the data plane and control plane, and records the

detected errors into system logs. You can check the logs to monitor LSP connectivity.

If both BFD and periodic MPLS traceroute are configured for an LSP and the periodic traceroute function

detects a data plane and control plane inconsistency, the device deletes the BFD session for the LSP and

re-establishes the BFD session based on the control plane.

MPLS BFD

MPLS BFD uses a BFD session to proactively verify the connectivity of an LSP tunnel or an MPLS TE tunnel.