Which tool identifies the point of failure in a P2MP LSP from the ingress LSR?
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A. B. C. D.C.
https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r5-3/mpls/configuration/guide/b-mpls-cg53x-asr9k/b-mpls-cg53x-The correct answer to the question is C. P2MP traceroute.
In a Point-to-Multipoint (P2MP) Label Switched Path (LSP) setup, the Ingress Label Switch Router (LSR) is responsible for sending packets to multiple egress LSRs over a single LSP. The P2MP LSP is established using Multiprotocol Label Switching (MPLS) and is used for efficient multicast transmission of data.
If there is a point of failure in a P2MP LSP from the ingress LSR, it becomes essential to identify the location of the failure to fix it. The P2MP traceroute tool is used for this purpose. It identifies the path taken by the P2MP LSP, the transit LSRs, and the egress LSRs that the packets are being forwarded to.
P2MP traceroute works by sending User Datagram Protocol (UDP) packets with specific Time-to-Live (TTL) values. Each time the packet reaches an LSR, the TTL value decreases, and the LSR sends an ICMP Time Exceeded message back to the source indicating that the packet has been dropped due to the TTL value reaching zero. The source then knows the IP address of the LSR that dropped the packet, and this information can be used to identify the point of failure in the P2MP LSP.
Option A, Jitter TLV, is used for measuring the variation in packet delay across a network path. It is not used for identifying the point of failure in a P2MP LSP.
Option B, SPAN, is used for monitoring network traffic by mirroring traffic from one port to another. It is not used for identifying the point of failure in a P2MP LSP.
Option D, P2MP ping, is used for testing the reachability of egress LSRs in a P2MP LSP. It is not used for identifying the point of failure in a P2MP LSP.