easyMultiple ChoiceObjective-mapped
CISA Practice Question: Refer to the exhibit
Exhibit
Access Control List (ACL) applied to interface GigabitEthernet0/0: permit ip host 10.0.0.1 any deny ip 10.0.0.0/24 any permit ip any any
Refer to the exhibit. An auditor reviews the ACL and notes that it allows traffic from a specific host while blocking other IPs in the same subnet. What is the most likely security issue?
⚠ Common exam trap
Candidates often assume that a 'deny' statement earlier in the ACL will block traffic regardless of later 'permit any' statements, but Cisco ACLs process rules sequentially and the first match wins, so the 'permit any' overrides the deny.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL is misconfigured because the permit any at the end bypasses the deny.
The ACL has a 'permit any' statement at the end, which overrides the preceding 'deny' statements. In Cisco ACLs, packets are processed sequentially from top to bottom; once a match is found, no further rules are evaluated. Therefore, the 'deny' for the subnet is never reached, and all traffic (including from the blocked subnet) is permitted, defeating the intended restriction.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The ACL blocks all traffic from the subnet except the host, which is desired.
Why it's wrong here
The desired effect is not achieved because the final permit any allows all traffic.
- ✓
The ACL is misconfigured because the permit any at the end bypasses the deny.
Why this is correct
Correct. The permit any at the end makes the deny rule redundant, allowing all traffic from the subnet.
- ✗
The ACL allows all traffic from the specific host, which is a risk.
Why it's wrong here
While allowing a specific host can be a risk, the greater issue is that the deny is bypassed.
- ✗
The ACL should be reversed to deny first.
Why it's wrong here
Reversing the order would still have issues; the permit any should be removed or restricted.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISA practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISA exam.