Chapter 6 Implementing Mpls Oam; Implementing Mpls Oam; Mpls Lsp Ping - Cisco NCS 5500 Series Configuration Manual

Implementing MPLS OAM

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Implementing MPLS OAM
MPLS Operations, Administration, and Maintenance (OAM) helps service providers to monitor label-switched
paths (LSPs) and quickly isolate MPLS forwarding problems to assist with fault detection and troubleshooting
in an MPLS network. This module describes MPLS LSP Ping and Traceroute features which can be used for
failure detection and troubleshooting of MPLS networks.

MPLS LSP Ping

The MPLS LSP Ping feature is used to check the connectivity between Ingress LSR and egress LSRs along
an LSP. MPLS LSP ping uses MPLS echo request and reply messages, similar to Internet Control Message
Protocol (ICMP) echo request and reply messages, to validate an LSP. While ICMP echo request and reply
messages validate IP networks, MPLS echo and reply messages validate MPLS networks. The MPLS echo
request packet is sent to a target router through the use of the appropriate label stack associated with the LSP
to be validated. Use of the label stack causes the packet to be forwarded over the LSP itself. The destination
IP address of the MPLS echo request packet is different from the address used to select the label stack. The
destination IP address is defined as a 127.x.y.z/8 address and it prevents the IP packet from being IP switched
to its destination, if the LSP is broken.
An MPLS echo reply is sent in response to an MPLS echo request. The reply is sent as an IP packet and it is
forwarded using IP, MPLS, or a combination of both types of switching. The source address of the MPLS
echo reply packet is an address obtained from the router generating the echo reply. The destination address
is the source address of the router that originated the MPLS echo request packet. The MPLS echo reply
destination port is set to the echo request source port.
Implementing MPLS OAM, page 59
MPLS OAM Using Nil FEC, page 62
MPLS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
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