- A
Custom routes must be created to direct traffic to a specific NIC using the VM's IP as next hop.
This allows traffic to be forwarded to the appliance for inspection.
- B
The VM must have an external IP on each NIC.
Why wrong: External IPs are not required for routing.
- C
The VM must have IP forwarding disabled.
Why wrong: IP forwarding must be enabled for the VM to route traffic between NICs.
- D
All NICs must be in the same subnet.
Why wrong: They must be in different subnets to isolate traffic.
Question 371 of 1,000
PCNE Implementing VPC Instances Practice Question
This PCNE practice question tests your understanding of implementing vpc instances. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You are deploying a third-party network appliance (e.g., firewall) in a GCP VPC. The appliance requires multiple network interfaces for traffic isolation. You create a VM with three NICs in different subnets. What is a key consideration for routing traffic through the appliance?
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
✓
Custom routes must be created to direct traffic to a specific NIC using the VM's IP as next hop.
Each NIC in a multi-NIC VM is assigned to a different subnet. By default, the VM only sends traffic out of the NIC that matches the destination subnet's route. To route traffic through a specific NIC, custom routes with next hop set to the VM's IP on that NIC are required.
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.
- ✓
Custom routes must be created to direct traffic to a specific NIC using the VM's IP as next hop.
Why this is correct
This allows traffic to be forwarded to the appliance for inspection.
Related concept
CIDR notation defines the prefix length.
- ✗
The VM must have an external IP on each NIC.
Why it's wrong here
External IPs are not required for routing.
- ✗
The VM must have IP forwarding disabled.
Why it's wrong here
IP forwarding must be enabled for the VM to route traffic between NICs.
- ✗
All NICs must be in the same subnet.
Why it's wrong here
They must be in different subnets to isolate traffic.
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.
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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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Implementing VPC Instances — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing VPC Instances — This question tests Implementing VPC Instances — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Custom routes must be created to direct traffic to a specific NIC using the VM's IP as next hop. — Each NIC in a multi-NIC VM is assigned to a different subnet. By default, the VM only sends traffic out of the NIC that matches the destination subnet's route. To route traffic through a specific NIC, custom routes with next hop set to the VM's IP on that NIC are required.
What should I do if I get this PCNE 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 PCNE 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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Last reviewed: Jul 4, 2026
This PCNE 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 PCNE exam.
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