mediumMultiple Choice
CAS-004 Practice Question: Refer to the exhibit
Exhibit
access-list extended OUTSIDE-IN permit tcp any host 10.0.1.100 eq 443 permit tcp any host 10.0.1.100 eq 8443 deny ip any any
Refer to the exhibit. A security analyst notices that users from the internet can reach the web server at 10.0.1.100 on port 443, but they cannot reach it on port 8443. What is the most likely cause?
⚠ Common exam trap
CAS-005 often tests the assumption that any unreachable port is a firewall problem, when the actual cause is frequently a service not listening on that port.
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 web server is not listening on port 8443
If users can reach the web server on port 443 but not on 8443, the firewall is clearly permitting traffic to that host, so the most likely cause is that the web server process is not listening on port 8443. A service that is not bound to a port cannot accept connections regardless of firewall rules, which explains why one port works and the other does not.
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 only permits traffic from specific source IPs
Why it's wrong here
Source-IP restrictions would equally affect port 443, since the same internet clients reach it successfully. Source-scoped ACLs suit restricting administrative access to known management subnets; here the differing behaviour between two ports on one host rules that out.
- ✗
The firewall rule order is incorrect
Why it's wrong here
Rule order only matters when overlapping rules conflict; a missing 8443 permit is absent regardless of sequence. Ordering errors suit shadowed or contradictory entries, whereas the stem shows 443 permitted and 8443 simply not allowed.
- ✓
The web server is not listening on port 8443
Why this is correct
Port 443 succeeds while 8443 fails, and both traverse the same network path to 10.0.1.100, so filtering cannot explain the asymmetry. The differing element is the listening socket: if no process binds 8443, the host returns TCP RST, making the service unreachable regardless of firewall rules.
- ✗
The firewall is blocking all traffic on port 8443
Why it's wrong here
A blanket block on 8443 would also deny any other service using that port, yet the stem gives no evidence of such a rule. Port-wide denial suits deliberate service decommissioning; the scenario points to a rule matching 443 specifically, leaving 8443 unmatched.
About these practice questions
This CAS-005 question is part of Courseiva's 973-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.