Refer to the exhibit. Customer B has decided not to receive any routes from R1 that originated outside the AS 100. Which AS path access list must the engineer choose to meet this requirement?
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Question 616
Correct Answer: B
To ensure that Customer B does not receive any routes from R1 that originated outside the AS 100, the AS path access list needs to match routes where AS 100 is the only AS in the path. The correct AS path regex for this requirement is '^100$', meaning that the path should start and end with AS 100, with no other AS numbers in between. Therefore, option B is the correct answer.
Discussion
dapardoOption: B
Agree with Vitalizator, B is the right one
vitalizatorOption: B
Correct answer is B since AS100 is the neighboring AS of R6 so it will be always the 1st in the AS path, and we don't want to see any other AS behind AS100, so it has to be ^100$
PietjeplukgelukOption: B
Indeed B is correct (Agree with Vitalizator & dapardo)