Firewall ACL Deny Action and Sequential Processing

Quick Answer

The answer is that the firewall denied the traffic from 10.0.1.15 to 10.0.2.10. This is correct because the firewall’s access control list (ACL) processes rules sequentially, and the first matching rule for this traffic is a deny action that explicitly blocks the source IP 10.0.1.15. In sequential processing, once a deny rule matches, the packet is dropped immediately without evaluating any subsequent rules, even if later rules would permit the traffic. On the ISC2 Certified in Cybersecurity CC exam, this concept tests your understanding of ACL order of operations and how a firewall applies a deny action as the decisive factor. A common trap is assuming that a permit rule later in the list overrides an earlier deny, but sequential processing means the first match wins. Remember the memory tip: “First match, final action”—the rule that matches first determines the packet’s fate, so a deny early in the list blocks all matching traffic regardless of later permits.