The answer is that the ACL blocks all ping requests. This is correct because the ACL, applied to the external interface, explicitly denies ICMP type 8 (echo-request) packets while permitting ICMP type 0 (echo-reply) packets, effectively stopping inbound ping requests but allowing replies for traffic initiated from inside the network. On the Systems Security Certified Practitioner SSCP exam, this scenario tests your understanding of how ACLs filter specific ICMP message types at the network perimeter, a common topic in the Access Controls domain. A frequent trap is assuming that blocking ICMP entirely stops all ping-related traffic, but the key distinction here is that only the request is blocked, not the reply. To remember this, think of ICMP type 8 as the “outgoing question” and type 0 as the “incoming answer”—the ACL silences the question while letting the answer through.
SSCP Network and Communications Security Practice Question
This SSCP practice question tests your understanding of network and communications security. 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 icmp any any echo-request
access-list 100 permit ip any any
!
interface GigabitEthernet0/0
ip access-group 100 in
Refer to the exhibit. An administrator applies this ACL to the external interface. What specific traffic is blocked?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
All ping requests
The ACL is applied to the external interface and denies ICMP echo-request (type 8) packets while permitting ICMP echo-reply (type 0) packets. This blocks only ping requests (echo-requests) from entering the network, but allows ping replies (echo-replies) to return for outbound-initiated traffic. Therefore, option D is correct because the ACL specifically targets and blocks all ping requests.
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.
✗
Both ping requests and replies
Why it's wrong here
Only echo-request is denied; echo-reply is permitted.
Only echo-request is denied; other ICMP types (e.g., echo-reply, destination unreachable) are permitted.
✓
All ping requests
Why this is correct
The deny statement blocks all ICMP echo-request messages, i.e., ping requests.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume 'ping' is a single protocol or that blocking ping requests also blocks replies, but Cisco tests the distinction between ICMP echo-request (type 8) and echo-reply (type 0) in ACLs.
Detailed technical explanation
How to think about this question
ICMP echo-request (type 8) and echo-reply (type 0) are separate protocol types in the ICMP header; ACLs can filter based on these type numbers. In a typical stateful firewall scenario, blocking inbound echo-requests prevents external hosts from pinging internal hosts, but outbound pings still work because the return traffic (echo-reply) is permitted. This is a common security practice to prevent network reconnaissance while maintaining functionality for internal diagnostics.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network and Communications Security — This question tests Network and Communications Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: All ping requests — The ACL is applied to the external interface and denies ICMP echo-request (type 8) packets while permitting ICMP echo-reply (type 0) packets. This blocks only ping requests (echo-requests) from entering the network, but allows ping replies (echo-replies) to return for outbound-initiated traffic. Therefore, option D is correct because the ACL specifically targets and blocks all ping requests.
What should I do if I get this SSCP 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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