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Exam 300-410 topic 1 question 391 discussion

Actual exam question from Cisco's 300-410

Question #: 391
Topic #: 1

Refer to the exhibit. The Customer Edge router (AS 65500) wants to use AS 100 as the preferred ISP for all external routes.

Customer Edge -
route-map SETLP
set local-preference 111
!
router bgp 65500
neighbor 192.168.111.1 remote-as 100
neighbor 192.168.111.1 route-map SETLP out
neighbor 192.168.112.2 remote-as 200

This configuration failed to send routes to AS 100 as the preferred path. Which set of configurations resolves the issue?

A. route-map SETLP
set local-preference 111
!
router bgp 65500
neighbor 192.168.111.1 remote-as 100
neighbor 192.168.111.1 route-map SETLP in
B. route-map SETPP
set as-path prepend 100 100
!
router bgp 65500
neighbor 192.168.111.1 remote-as 100
neighbor 192.168.111.1 route-map SETPP in
C. route-map SETPP
set as-path prepend 111 111
!
router bgp 65500
neighbor 192.168.111.1 remote-as 100
neighbor 192.168.111.1 route-map SETPP out
D. route-map SETLP
set local-preference 111
!
router bgp 65500
neighbor 192.168.111.1 remote-as 100
neighbor 192.168.111.1 route-map SETLP out

Show Suggested Answer

Suggested Answer: A 🗳️

by mitosenoriko at Jan. 8, 2023, 9:36 p.m.

Comments

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Slinky

Highly Voted 2 years, 2 months ago

Selected Answer: A

You apply local pref in the inbound direction so that all externally learned prefixes are preferred from that neighbor within your AS.

upvoted 7 times

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drxz

Highly Voted 2 years, 2 months ago

Selected Answer: A

Answer is A. It states that the configuration failed to send routes to AS100 as the preferred path. You need to swap the in to out on the routemap. with answer b you are just extending the AS path making it less desirable. which is also for incoming traffic, not outgoing.

upvoted 7 times

Slinky

2 years, 2 months ago

This is the correct answer. B is NOT it.

upvoted 1 times

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NZhang

Most Recent 1 year, 3 months ago

I would like to say, none of the answer is correct. Local Preference can only be sent to a iBGP peer, hence A and D are incorrect. As-path prepend should be done on ISB-B to achieve the object here, so A and C are wrong as well.

upvoted 1 times

XBfoundX

9 months ago

not true you are not sending the local preference you are modifying your inbound LP inside your AS when you are going to advertise this prefix to other neighbors you are gonna put the LP specified inbound and the other routers of the AS will use the path towords that router

upvoted 2 times

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bk989

1 year ago

Answer = A, Customer Edge is setting AS on received prefixes on his own router

upvoted 2 times

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Pietjeplukgeluk

1 year, 6 months ago

Selected Answer: A

This question can be simplified by using plain english: The goal is to "prefer ISP AS100" for all outbound traffic?

upvoted 2 times

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ZamanR

1 year, 7 months ago

A is correct

upvoted 1 times

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guy276465281819372

2 years ago

Selected Answer: A

A correct

upvoted 3 times

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inteldarvid

2 years ago

Selected Answer: A

100% option A correct

upvoted 2 times

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HungarianDish_111

2 years, 2 months ago

Selected Answer: A

We set a Local Preference of 111 to all prefixes learned from the neighbor 192.168.111.1 (AS 100), and so we make that path preferable. https://community.cisco.com/t5/networking-knowledge-base/understanding-bgp-best-path-selection-manipulation/ta-p/3150576

upvoted 4 times

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6dd4aa0

2 years, 3 months ago

A is the answer. It cannot be B because in doing so, the AS-PATH will contain "100 100 100". This will make as though it will need additional 2 more paths to reach there!

upvoted 2 times

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