•
Configure traffic engineering features on the headend, midpoint, and tailend routers in the MPLS network
•
Enable MPLS OAM using the mpls oam command on all routers in the MPLS network
MPLS Network Management with MPLS LSP Ping and MPLS
LSP Traceroute
To manage an MPLS network, you must have the ability to monitor LSPs and quickly isolate MPLS forwarding
problems. You need ways to characterize the liveliness of an LSP and reliably detect when an LSP fails to
deliver user traffic.
You can use MPLS LSP ping to verify the LSP that is used to transport packets. You can use MPLS LSP
traceroute to trace LSPs that are used to carry packets destined for P2MP LSP.
An MPLS echo request is sent through an LSP to validate it. A TTL expiration or LSP breakage causes the
transit router to process the echo request before it gets to the intended destination. The router returns an MPLS
echo reply that contains an explanatory reply code to the originator of the echo request.
The successful echo request is processed at the egress of the LSP. The echo reply is sent through an IP path,
an MPLS path, or a combination of both, back to the originator of the echo request.
Roles of Various Routers
A P2MP TE network contains the following elements:
•
Headend Router
The headend router, also called the source or ingress router, is responsible for initiating the signaling
messages that set up the P2MP TE LSP. The headend router can also be a branch point, which means
the router performs packet replication and the sub-LSPs split into different directions.
•
Midpoint Router
The midpoint router is where the sub-LSP signaling is processed. The midpoint router can be a branch
point.
•
Tailend Router
The tailend router, also called the destination, egress, or leaf-node router, is where sub-LSP signaling
ends. The router which is one of potentially many destinations of the P2MP TE LSP.
•
Bud Router
A bud router is a midpoint and tailend router at the same time. An LSR that is an egress LSR, but also
has one or more directly connected downstream LSRs.
•
Branch Router
A branch router is either a midpoint or tailend router at any given time.
•
Transit Router
A transit router is an LSR that is not an egress router, but also has one or more directly connected
downstream routers.
•
A P2MP tunnel consists of one or more sub-LSPs.All sub-LSPs belonging to the same P2MP tunnel
employ the same constraints, protection policies, and so on, which are configured at the headend router.
Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router, Release 5.1.x
396
Implementing MPLS OAM
MPLS Network Management with MPLS LSP Ping and MPLS LSP Traceroute
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