Exam 400-007 topic 1 question 43 discussion

Actual exam question from Cisco's 400-007

Question #: 43
Topic #: 1

Refer to the exhibit. An engineer is designing the network for a multihomed customer running in AS 111 AS 111 does not have any other ASs connected to it.
Which technology is more comprehensive to use in the design to make sure that the AS is not being used as a transit AS?

A. Include an AS path access list to send routes to the neighboring ASs that only have AS 111 in the AS path field.
B. Configure the AS-set attribute to allow only routes from AS 111 to be propagated to the neighbor ASs.
C. Use the local preference attribute to configure your AS as a "non-transit" AS.
D. Include a prefix list to only receive routes from neighboring ASs.

Show Suggested Answer

Suggested Answer: A 🗳️

by re_j0hn at June 28, 2023, 6:54 a.m.

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Devsin2000

3 months ago

Selected Answer: A

To make it non-transitive, we must not advertise the routes that are received from other ASs AS Path filter is an excellent tool to do that.

upvoted 1 times

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644143b

9 months, 3 weeks ago

Selected Answer: A

outgoing towards peer AS -> permit ^$ (empty as-path)

upvoted 1 times

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BrianWei

1 year, 10 months ago

I do think B is correct as A still will propagate route where learnt from other BGP AS, it could potentially result AS111 as transit AS.

upvoted 1 times

DDDDFFFF

1 year, 9 months ago

If the route is learnt from other AS, it should have other AS no. in the AS path, i.e. not only AS111. Hence answer A is correct.

upvoted 3 times

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re_j0hn

1 year, 10 months ago

A is correct answer. Can be achieved in few ways. Filter-list with AS PATH access-list. No-Export Community Prefix-list Filtering Distribute-list Filtering

upvoted 1 times

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Exam 400-007 topic 1 question 43 discussion

Comments

Devsin2000

644143b

BrianWei

DDDDFFFF

re_j0hn

SY0-701