Question 110
At Seabright Municipal Works, a team reports that it corrected the following problem affecting public service networks and records: A NAT gateway changes IPsec peer addresses and native ESP traffic fails through the path. Which observation BEST verifies that the correction actually worked?
Explanation
Correct Answer
A tunnel behind NAT establishes and carries protected traffic without ESP being dropped. This is the decisive evidence for the original problem: A NAT gateway changes IPsec peer addresses and native ESP traffic fails through the path. It verifies that the intended corrective control—Use supported IPsec NAT traversal with UDP encapsulation and matching peer configuration—works in the relevant environment; a completed change ticket alone would not prove the outcome at Seabright Municipal Works.
Incorrect Answers
Credential storage contains salted adaptive hashes rather than plaintext or fast unsalted digests. This would be relevant evidence for a different failure: A security team assumes a fast general-purpose hash can safely protect stored user passwords by itself, usually addressed by Use an adaptive password-hashing function with unique salts and suitable work factors. It does not demonstrate that the current problem at Seabright Municipal Works was resolved. The specific required evidence is: A tunnel behind NAT establishes and carries protected traffic without ESP being dropped.
The negotiated security associations protect bidirectional traffic and are visible in VPN status. This would be relevant evidence for a different failure: Two remote offices require confidentiality and authenticated integrity for traffic traversing the public Internet, usually addressed by Configure standards-based IPsec using appropriate IKE authentication and encryption proposals. It does not demonstrate that the current problem at Seabright Municipal Works was resolved. The specific required evidence is: A tunnel behind NAT establishes and carries protected traffic without ESP being dropped.
A controlled pilot negotiates supported algorithms and documents rollback and interoperability. This would be relevant evidence for a different failure: A long-lived cryptographic system has no plan for migration to quantum-resistant key establishment, usually addressed by Inventory vulnerable algorithms and plan interoperable standards-based post-quantum or hybrid migration. It does not demonstrate that the current problem at Seabright Municipal Works was resolved. The specific required evidence is: A tunnel behind NAT establishes and carries protected traffic without ESP being dropped.