Question 540
During a security incident tabletop exercise at Harbor Point Medical, engineers say that they resolved this finding: An FTD tunnel has healthy SAs but one internal subnet cannot reach the remote peer. Which result provides the STRONGEST acceptance evidence?
Explanation
Correct Answer
Traffic from each approved subnet crosses the tunnel and unrelated networks stay blocked. This is the decisive evidence for the original problem: An FTD tunnel has healthy SAs but one internal subnet cannot reach the remote peer. It verifies that the intended corrective control—Inspect routing, protected network selectors, access control, and NAT treatment for that subnet—works in the relevant environment; a completed change ticket alone would not prove the outcome at Harbor Point Medical.
Incorrect Answers
The VPN remains established through NAT with reliable bidirectional protected flows. This would be relevant evidence for a different failure: A tunnel drops traffic only when behind a NAT device that changes the peer's translated address, usually addressed by Verify NAT traversal configuration and peer reachability for UDP-encapsulated IPsec. It does not demonstrate that the current problem at Harbor Point Medical was resolved. The specific required evidence is: Traffic from each approved subnet crosses the tunnel and unrelated networks stay blocked.
IKE establishes successfully and logs show compatible negotiated parameters. This would be relevant evidence for a different failure: An FTD site-to-site VPN shows no active IKE security association despite route reachability, usually addressed by Inspect IKE proposals, peer identity, authentication, and exchange logs before changing data-plane policy. It does not demonstrate that the current problem at Harbor Point Medical was resolved. The specific required evidence is: Traffic from each approved subnet crosses the tunnel and unrelated networks stay blocked.
Negotiation succeeds with the current credential while the old PSK remains invalid. This would be relevant evidence for a different failure: Site-to-site VPN negotiation repeatedly fails just after a PSK rotation, usually addressed by Check secure peer key agreement and effective authentication profile on both sides. It does not demonstrate that the current problem at Harbor Point Medical was resolved. The specific required evidence is: Traffic from each approved subnet crosses the tunnel and unrelated networks stay blocked.