CISSP Security Architecture and Engineering Practice Question
This CISSP practice question tests your understanding of security architecture and engineering. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
access-list 100 deny tcp host 10.1.1.2 any eq 80
access-list 100 permit tcp any any eq 80
access-list 100 deny ip any any
Refer to the exhibit. What is the effect of this ACL when applied inbound to an interface?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Traffic from host 10.1.1.2 to port 80 is denied, but others allowed
Option C is correct because the ACL explicitly denies traffic from host 10.1.1.2 to any destination on TCP port 80, and then permits all other IP traffic. Since the ACL is applied inbound, it filters traffic before routing, and the implicit deny at the end only blocks traffic that does not match any permit statement. Thus, only the specific host-to-port-80 traffic is denied, and all other traffic is permitted.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
All traffic is denied
Why it's wrong here
Some traffic (port 80 from non-10.1.1.2) is permitted.
✗
Only traffic from host 10.1.1.2 to port 80 is denied, all other traffic permitted
Why it's wrong here
The third line denies all other traffic (non-port 80), so not all other traffic is permitted.
✓
Traffic from host 10.1.1.2 to port 80 is denied, but others allowed
Why this is correct
Correct. The first line denies 10.1.1.2 to port 80; the second permits others to port 80.
Related concept
Read the scenario before looking for a memorised answer.
✗
All traffic to port 80 is denied
Why it's wrong here
Traffic to port 80 from sources other than 10.1.1.2 is permitted.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often forget the implicit deny at the end of an ACL and mistakenly think the deny entry blocks all traffic to port 80, or they misread the order and assume the permit ip any any does not override the deny for other sources.
Detailed technical explanation
How to think about this question
Cisco ACLs process entries sequentially from top to bottom; once a match is found, no further entries are evaluated. The deny tcp host 10.1.1.2 any eq 80 entry matches only packets with source IP 10.1.1.2 and destination TCP port 80, and the subsequent permit ip any any allows all other traffic. The implicit deny ip any any at the end of every ACL is only reached if no prior permit matches, but here the permit covers all remaining traffic. In real-world scenarios, this ACL might be used to block a specific host from accessing web servers while allowing all other hosts full access.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Traffic from host 10.1.1.2 to port 80 is denied, but others allowed — Option C is correct because the ACL explicitly denies traffic from host 10.1.1.2 to any destination on TCP port 80, and then permits all other IP traffic. Since the ACL is applied inbound, it filters traffic before routing, and the implicit deny at the end only blocks traffic that does not match any permit statement. Thus, only the specific host-to-port-80 traffic is denied, and all other traffic is permitted.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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