Exam 350-501 topic 1 question 250 discussion

Actual exam question from Cisco's 350-501

Question #: 250
Topic #: 1

Refer to the exhibit. An engineer configured R6 as the headend LSR of an RSVP-TE LSP to router XR2, with the dynamic path signaled as R6-R2-R5-XR2, and set the OSPF cost of all links to 1. MPLS autotunnel backup is enabled on all routers to protect the LSP. Which two NNHOP backup tunnels should the engineer use to complete the implementation? (Choose two.)

A. The R2 backup tunnel path R2-R1-R4-XR1-XR2.
B. The R2 backup tunnel path R2-R5 across the alternate link.
C. The R6 backup tunnel path R6-R2-R5.
D. The R6 backup tunnel path R6-R1-R4-R5.
E. The R6 backup tunnel path R6-R1-R2.

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Suggested Answer: AD 🗳️

by 12_sdeEQ at April 5, 2023, 5:06 p.m.

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hicah14861

10 months ago

Selected Answer: AD

NNHOP means node-protection. As we have two transit nodes, we need to take into consideration what happens when they go down. These two are R2 and R5. If R2 goes down, we need to go R6 --> R1 --> R4 --> R5 (This is the fastest) If R5 goes down, we need to go R6 --> R2 --> R1 --> R4 --> XR1 --> XR2 The reason for this is becasue R2 is going to be the one who detects that R5 went down so it will re-reoute the traffic, even though there would be a better path.

upvoted 3 times

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12_sdeEQ

1 year, 10 months ago

Selected Answer: AD

I agree, NNHOP provide node protetion , since the primary path from R6 to XR2 pass through R2 and R5 , the role of bgp autotunnel with NNHOP is to protect the LSP in case one of those two nodes fails, -option A provide protection of LSP in case of R5 fails -option D provide protection of LSP in case of R2 fails -options B, C and E dont provide a protection in case of R2 or R5 fails , so are all wrong

upvoted 3 times

frz007

1 year, 8 months ago

can you please tell why not B

upvoted 1 times

avinish87m

1 year, 7 months ago

NNHOP--Protects against node failure

upvoted 2 times

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