Question 250
An operator attaches a standard BGP community to customer routes. Observed: The upstream does not apply the agreed blackhole policy. What evidence would validate recovery from this precise failure mode?
Explanation
Correct Answer
The intended result is The upstream confirms the intended tagged route receives the agreed action. It specifically verifies recovery from the carrier expects a different community value or route export suppresses communities, which produced the original symptom: The upstream does not apply the agreed blackhole policy. It is stronger evidence than a generic interface-up indicator.
Incorrect Answers
This result is useful in another case with evidence One router silently sources TCP from a physical interface instead of its loopback. It does not test recovery from the upstream does not apply the agreed blackhole policy. Check instead whether the upstream confirms the intended tagged route receives the agreed action.
It confirms an unrelated service correction: Client and nonclient relationships were modified without controlling reflection loops. The present case reports The upstream does not apply the agreed blackhole policy. Its completion test is The upstream confirms the intended tagged route receives the agreed action.
That observation would verify a separate fault involving standard communities do not provide the three-field large-community semantics. Its symptom is A 32-bit community representation cannot encode the required triple of values. For this case the actual issue is the carrier expects a different community value or route export suppresses communities, and the relevant success signal is The upstream confirms the intended tagged route receives the agreed action.