- A
A health check must be configured for the backend service.
Health checks are required to determine instance health.
- B
A firewall rule must allow traffic from the proxy-only subnet.
Why wrong: ILB uses the health check firewall rules, not a proxy subnet.
- C
The forwarding rule's IP address must be from the host project's subnet.
Why wrong: The IP can be from any subnet in the service project.
- D
The load balancer forwarding rule must be in the same region as the backend instances.
ILB is regional.
- E
Global routing must be enabled in the VPC.
Why wrong: ILB does not require global routing.
Question 299 of 1,000
mediumMultiple SelectObjective-mapped
Internal TCP/UDP Load Balancer Requirements in Shared VPC
This PCNE practice question tests your understanding of pcne exam topics. 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.
Which TWO of the following are required when setting up an internal TCP/UDP load balancer (ILB) in a shared VPC environment?
Quick Answer
The answer is that the load balancer forwarding rule must be in the same region as the backend instances, and the backend service must reference a health check. These two requirements are fundamental because an internal TCP/UDP load balancer operates regionally, not globally, so the forwarding rule and its backend VMs must reside within the same regional scope to route traffic correctly. The health check is mandatory to determine instance health and ensure traffic is only sent to responsive backends. On the Google Professional Cloud Network Engineer exam, this question tests your understanding of shared VPC constraints, where a common trap is assuming the load balancer needs an IP from the host project or that global routing applies. Remember that ILB is strictly regional, and unlike HTTP load balancers, it does not use proxy subnets. A useful memory tip: think "same region, healthy backends" — the forwarding rule and health check are the two non-negotiable pillars for any internal TCP/UDP load balancer in a shared VPC.
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
✓
A health check must be configured for the backend service.
Correct answers: A and D. A: A health check is mandatory for an internal TCP/UDP load balancer (ILB) backend service to determine instance health. D: The ILB forwarding rule must be in the same region as the backend instances because ILB is a regional load balancer. B: Incorrect. ILB does not use proxy-only subnets; firewall rules for proxy-only subnets are required only for load balancers that use Envoy proxies (e.g., HTTP(S) LB). C: Incorrect. While the forwarding rule's IP address is taken from a subnet in the shared VPC (owned by the host project), this is not a separate requirement; the critical requirement is that the forwarding rule and backends are in the same region. E: Incorrect. Global routing is not needed for ILB; it operates within a single region.
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.
- ✓
A health check must be configured for the backend service.
Why this is correct
Health checks are required to determine instance health.
Related concept
CIDR notation defines the prefix length.
- ✗
A firewall rule must allow traffic from the proxy-only subnet.
Why it's wrong here
ILB uses the health check firewall rules, not a proxy subnet.
- ✗
The forwarding rule's IP address must be from the host project's subnet.
Why it's wrong here
The IP can be from any subnet in the service project.
- ✓
The load balancer forwarding rule must be in the same region as the backend instances.
Why this is correct
ILB is regional.
Related concept
CIDR notation defines the prefix length.
- ✗
Global routing must be enabled in the VPC.
Why it's wrong here
ILB does not require global routing.
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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this PCNE question test?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: A health check must be configured for the backend service. — Correct answers: A and D. A: A health check is mandatory for an internal TCP/UDP load balancer (ILB) backend service to determine instance health. D: The ILB forwarding rule must be in the same region as the backend instances because ILB is a regional load balancer. B: Incorrect. ILB does not use proxy-only subnets; firewall rules for proxy-only subnets are required only for load balancers that use Envoy proxies (e.g., HTTP(S) LB). C: Incorrect. While the forwarding rule's IP address is taken from a subnet in the shared VPC (owned by the host project), this is not a separate requirement; the critical requirement is that the forwarding rule and backends are in the same region. E: Incorrect. Global routing is not needed for ILB; it operates within a single region.
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: Jun 24, 2026
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