The answer is that the ACL blocks all RFC 1918 private addresses, which likely includes the cloud VPC CIDR range. This is correct because cloud environments commonly assign private IP addresses from the 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16 ranges to their virtual instances. When a Cisco ASA firewall in the cloud applies an ACL denying these RFC 1918 ranges, any on-premises traffic destined for a cloud instance using a private IP within those blocks is dropped, breaking connectivity. On the Cisco SCOR / CCNP Security Core 350-701 exam, this scenario tests your understanding of how cloud ACLs interact with overlapping private address spaces, a common trap where students overlook that cloud VPCs often use non-routable RFC 1918 addresses. A key memory tip: think of the ACL as a “cloud gate” that mistakenly blocks your own private neighborhood—if the cloud VPC lives on a 10.x.x.x street, a deny for 10.0.0.0/8 locks the door.
350-701 Cloud Security Practice Question
This 350-701 practice question tests your understanding of cloud security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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
ip access-list extended CLOUD-FILTER
deny ip 10.0.0.0 0.255.255.255 any
deny ip 172.16.0.0 0.15.255.255 any
deny ip 192.168.0.0 0.0.255.255 any
permit ip any any
Refer to the exhibit. A Cisco ASA firewall is deployed in a cloud environment. After applying this ACL to an interface, users report that they cannot access cloud instances from on-premises. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
ip access-list extended CLOUD-FILTER
deny ip 10.0.0.0 0.255.255.255 any
deny ip 172.16.0.0 0.15.255.255 any
deny ip 192.168.0.0 0.0.255.255 any
permit ip any any
A
The ACL allows all traffic but users need NAT
Why wrong: ACL blocks traffic before NAT.
B
The ACL is applied to the wrong interface
Why wrong: Not indicated in the scenario.
C
The ACL blocks all RFC 1918 private addresses, which may include the cloud VPC CIDR
Cloud VPCs often use private IP ranges, which are denied.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL blocks all RFC 1918 private addresses, which may include the cloud VPC CIDR
Option C is correct because the ACL shown in the exhibit (which is not provided but implied by the question) blocks RFC 1918 private address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16). Cloud VPCs commonly use these private IP ranges for their instances. If the cloud VPC CIDR falls within an RFC 1918 range, the ACL will deny traffic to those cloud instances, preventing on-premises users from accessing them.
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.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume RFC 1918 blocks are safe for cloud environments, but cloud VPCs frequently use these private ranges, so blocking them breaks connectivity to cloud instances.
Trap categories for this question
Scenario analysis trap
Not indicated in the scenario.
Detailed technical explanation
How to think about this question
RFC 1918 defines private IPv4 address ranges that are not routable on the public internet but are commonly used in cloud VPCs (e.g., AWS VPCs default to 10.0.0.0/16). When a Cisco ASA ACL denies these ranges, it blocks all traffic to cloud instances using those addresses, even if the traffic is properly routed. In a cloud environment, the ASA often acts as a virtual firewall (e.g., Cisco ASAv) and must be configured to permit the specific VPC CIDR, not blindly block RFC 1918 addresses.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Cloud Security — This question tests Cloud Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ACL blocks all RFC 1918 private addresses, which may include the cloud VPC CIDR — Option C is correct because the ACL shown in the exhibit (which is not provided but implied by the question) blocks RFC 1918 private address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16). Cloud VPCs commonly use these private IP ranges for their instances. If the cloud VPC CIDR falls within an RFC 1918 range, the ACL will deny traffic to those cloud instances, preventing on-premises users from accessing them.
What should I do if I get this 350-701 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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