Question 360
A provider installs ECMP over two internal iBGP peers. Observed: Equal NLRI from different originators causes inconsistent distribution. Which ongoing validation gate would best detect a recurrence of this problem?
Explanation
Correct Answer
A useful regression gate tests whether both permitted paths become active only when their attributes qualify and alerts when equal NLRI from different originators causes inconsistent distribution. This directly checks the technical weakness: Required BGP multipath attributes are not sufficiently equivalent for multipath. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.
Incorrect Answers
This gate monitors a different failure, one router silently sources tcp from a physical interface instead of its loopback. It would not detect the current problem: Equal NLRI from different originators causes inconsistent distribution. The appropriate check requires both permitted paths become active only when their attributes qualify.
The proposed control is tied to a broad routing-policy term matches routes outside its intended customer prefix list, typically observed when policy unexpectedly modifies MED for every customer route. Here the target is required bgp multipath attributes are not sufficiently equivalent for multipath; monitor both permitted paths become active only when their attributes qualify.
It is valid for another service scenario but checks the upstream does not apply the agreed blackhole policy. This case instead needs a gate for equal nlri from different originators causes inconsistent distribution and evidence that both permitted paths become active only when their attributes qualify.