- A
The firewall rule has a priority lower than 65535.
Why wrong: Lower priority numbers mean higher priority. If the rule has a priority of 1000, it is evaluated before rules with higher numbers. The default priority is 1000, which is fine.
- B
The instance is using a VPC with a custom subnet.
Why wrong: Custom subnets do not affect firewall rule applicability. Rules apply to instances based on tags, target service accounts, or entire network.
- C
The firewall rule is denying outbound traffic.
Why wrong: Firewall rules are stateful; if inbound is allowed, outbound return traffic is automatically allowed. A deny outbound rule would not affect inbound connections.
- D
The instance does not have the 'web-server' network tag.
The firewall rule targets instances with the 'web-server' tag. If the instance lacks this tag, the rule does not apply to it.
Google ACE Configuring Access and Security Practice Question
This ACE practice question tests your understanding of configuring access and 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.
An engineer created a firewall rule to allow inbound HTTP traffic on port 80 from the internet to instances with the tag 'web-server'. However, after applying the rule, a test instance with the tag 'web-server' is still not reachable on port 80. What is a likely cause?
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 instance does not have the 'web-server' network tag.
Firewall rules are stateful, meaning return traffic is automatically allowed, but only if the inbound connection is permitted. A common misconfiguration is that the rule targets the wrong network tag, the instance does not have the tag, or the rule is not applied to the correct VPC network. Another possible issue is a higher-priority deny rule blocking the traffic. However, the most direct cause is that the instance lacks the tag specified in the rule.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 firewall rule has a priority lower than 65535.
Why it's wrong here
Lower priority numbers mean higher priority. If the rule has a priority of 1000, it is evaluated before rules with higher numbers. The default priority is 1000, which is fine.
- ✗
The instance is using a VPC with a custom subnet.
Why it's wrong here
Custom subnets do not affect firewall rule applicability. Rules apply to instances based on tags, target service accounts, or entire network.
- ✗
The firewall rule is denying outbound traffic.
Why it's wrong here
Firewall rules are stateful; if inbound is allowed, outbound return traffic is automatically allowed. A deny outbound rule would not affect inbound connections.
- ✓
The instance does not have the 'web-server' network tag.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ACE subnetting questions on CIDR, address ranges, and subnet selection.
- →
Configuring Access and Security — study guide chapter
Learn the concepts, then practise the questions
- →
Configuring Access and Security practice questions
Targeted practice on this topic area only
- →
All ACE questions
1,000 questions across all exam domains
- →
Google Associate Cloud Engineer study guide
Full concept coverage aligned to exam objectives
- →
ACE practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related ACE practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Configuring Access and Security practice questions
Practise ACE questions linked to Configuring Access and Security.
Planning and Configuring a Cloud Solution practice questions
Practise ACE questions linked to Planning and Configuring a Cloud Solution.
Ensuring Successful Operation of a Cloud Solution practice questions
Practise ACE questions linked to Ensuring Successful Operation of a Cloud Solution.
Deploying and Implementing a Cloud Solution practice questions
Practise ACE questions linked to Deploying and Implementing a Cloud Solution.
Setting Up a Cloud Solution Environment practice questions
Practise ACE questions linked to Setting Up a Cloud Solution Environment.
ACE fundamentals practice questions
Practise ACE questions linked to ACE fundamentals.
ACE scenario practice questions
Practise ACE questions linked to ACE scenario.
ACE troubleshooting practice questions
Practise ACE questions linked to ACE troubleshooting.
Practice this exam
Start a free ACE practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this ACE question test?
Configuring Access and Security — This question tests Configuring Access and Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The instance does not have the 'web-server' network tag. — Firewall rules are stateful, meaning return traffic is automatically allowed, but only if the inbound connection is permitted. A common misconfiguration is that the rule targets the wrong network tag, the instance does not have the tag, or the rule is not applied to the correct VPC network. Another possible issue is a higher-priority deny rule blocking the traffic. However, the most direct cause is that the instance lacks the tag specified in the rule.
What should I do if I get this ACE question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ACE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This ACE practice question is part of Courseiva's free Google Cloud 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 ACE exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.