Question 520
During a planned service expansion at Atlas Scientific, engineers say that they resolved this finding: IKE succeeds but there are no IPsec child SAs when users send protected traffic. Which result provides the STRONGEST acceptance evidence?
Explanation
Correct Answer
Corrected child SAs form and packet encryption and decryption counters increment. This is the decisive evidence for the original problem: IKE succeeds but there are no IPsec child SAs when users send protected traffic. It verifies that the intended corrective control—Compare IPsec proposals, traffic selectors, PFS settings, and the actual interesting traffic—works in the relevant environment; a completed change ticket alone would not prove the outcome at Atlas Scientific.
Incorrect Answers
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 Atlas Scientific was resolved. The specific required evidence is: Corrected child SAs form and packet encryption and decryption counters increment.
Protected traffic uses the intended encrypted path rather than an ordinary Internet route. This would be relevant evidence for a different failure: Tunnel SAs exist but packets reach a wrong next hop instead of the VPN egress interface, usually addressed by Correct routing and policy-based forwarding toward the appropriate protected tunnel. It does not demonstrate that the current problem at Atlas Scientific was resolved. The specific required evidence is: Corrected child SAs form and packet encryption and decryption counters increment.
Traffic from each approved subnet crosses the tunnel and unrelated networks stay blocked. This would be relevant evidence for a different failure: An FTD tunnel has healthy SAs but one internal subnet cannot reach the remote peer, usually addressed by Inspect routing, protected network selectors, access control, and NAT treatment for that subnet. It does not demonstrate that the current problem at Atlas Scientific was resolved. The specific required evidence is: Corrected child SAs form and packet encryption and decryption counters increment.