The correct answer is to reserve static external IP addresses and assign them to the Cloud NAT. This ensures high availability by allowing you to allocate multiple NAT IPs across different zones, so traffic continues if a zone fails, while static reservations prevent IP loss during gateway recreation—critical for firewall rules or DNS records that rely on fixed addresses. On the Google Professional Cloud Security Engineer exam, this tests your understanding that Cloud NAT is a regional resource, not zonal, and that dynamic IPs (option A) can change unexpectedly, breaking connectivity. A common trap is assuming you need one NAT gateway per zone, but a single regional gateway with multiple static IPs suffices. Remember the memory tip: “Static across zones keeps your NAT on its throne.”
PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A company is setting up Cloud NAT for a subnet that hosts compute instances. They want to ensure high availability and efficient use of IPs. Which TWO configurations should they apply? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Specify at least two NAT IPs, each from different zones for redundancy.
Options B and D are correct. Using multiple NATIPs in different zones provides HA, and manual NAT IP with static reservations ensures IPs are not lost. Option A is wrong because dynamic NAT IPs may change. Option C is wrong because one NAT gateway is sufficient per region; zone-level is not needed. Option E is wrong because Cloud NAT already handles port exhaustion.
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.
✗
Create a separate Cloud NAT gateway for each zone in the region.
Why it's wrong here
A single Cloud NATgateway per region can handle multiple zones; separate gateways are unnecessary.
✗
Disable IP masquerading to preserve source IPs.
Why it's wrong here
Disabling IP masquerading would break NAT functionality; Cloud NAT is designed to masquerade.
✓
Specify at least two NAT IPs, each from different zones for redundancy.
Why this is correct
Multiple IPs across zones provide HA if a zone fails.
Use dynamic NAT IPs so that Google-managed allocation is used.
Why it's wrong here
Dynamic IPs can change, causing issues with whitelisting.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 PCSE subnetting questions on CIDR, address ranges, and subnet selection.
Configuring network security — This question tests Configuring network security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Specify at least two NAT IPs, each from different zones for redundancy. — Options B and D are correct. Using multiple NAT IPs in different zones provides HA, and manual NAT IP with static reservations ensures IPs are not lost. Option A is wrong because dynamic NAT IPs may change. Option C is wrong because one NAT gateway is sufficient per region; zone-level is not needed. Option E is wrong because Cloud NAT already handles port exhaustion.
What should I do if I get this PCSE 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 PCSE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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This PCSE 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 PCSE exam.
Question Discussion
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