Question 240
A customer AS wants to favor inbound traffic through one of two links. Observed: External peers continue choosing the wrong ingress despite local preference changes. Which ongoing validation gate would best detect a recurrence of this problem?
Explanation
Correct Answer
A useful regression gate tests whether upstream route selection changes as validated by external path observations and alerts when external peers continue choosing the wrong ingress despite local preference changes. This directly checks the technical weakness: Local preference is not exported to other autonomous systems. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.
Incorrect Answers
The proposed control is tied to upstream local preference overrides the longer as-path signal, typically observed when new prepended announcements do not influence the chosen inbound route. Here the target is local preference is not exported to other autonomous systems; monitor upstream route selection changes as validated by external path observations.
It is valid for another service scenario but checks a stable recovered prefix stays suppressed after several route updates. This case instead needs a gate for external peers continue choosing the wrong ingress despite local preference changes and evidence that upstream route selection changes as validated by external path observations.
This gate monitors a different failure, a route arrives with the right community but enters the wrong routing instance. It would not detect the current problem: External peers continue choosing the wrong ingress despite local preference changes. The appropriate check requires upstream route selection changes as validated by external path observations.