The correct approach is to re-IP one of the VPC networks to a non-conflicting range and then use VPC Network Peering. This is required because VPC peering overlapping IP ranges is fundamentally incompatible—Google Cloud’s routing tables cannot distinguish between two subnets with identical CIDR blocks, so direct peering fails. Re-IPing one VPC to a unique range, such as 10.1.0.0/16, eliminates the conflict, allowing peering to deliver high throughput and low latency over Google’s internal backbone without bandwidth limits or single points of failure. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding that VPC peering is a layer-3 connection requiring non-overlapping ranges, a common trap where candidates mistakenly suggest VPNs or Shared VPC. Remember the memory tip: “No overlap, no problem—peering needs unique IPs to link.”
PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. 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.
A company needs to securely connect two VPC networks from different projects in the same organization. Each VPC has overlapping IP ranges (10.0.0.0/16). They require high throughput and low latency. What is the recommended approach?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Re-IP one of the VPC networks to a non-conflicting range and then use VPC Network Peering.
Option A is correct because VPC Network Peering requires non-overlapping IP ranges to establish direct connectivity. By re-IPing one VPC to a non-conflicting range (e.g., 10.1.0.0/16), you eliminate the routing conflict, allowing peering to provide high throughput and low latency via Google's internal backbone, with no bandwidth limits or single points of failure.
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.
✓
Re-IP one of the VPC networks to a non-conflicting range and then use VPC Network Peering.
Why this is correct
Re-IPing resolves the overlap and allows peering, which provides high throughput and low latency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Dedicated Interconnect to directly connect the two VPCs.
Why it's wrong here
Interconnect connects on-premises to VPC, not VPC to VPC; also does not solve overlapping.
✗
Use VPC Network Peering.
Why it's wrong here
VPC Peering requires non-overlapping IP ranges; overlapping will cause routing conflicts.
✗
Use HA VPN with dynamic routing.
Why it's wrong here
VPN also requires non-overlapping IP ranges for routing to work.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that VPC Network Peering can handle overlapping IP ranges if you use custom route tables or subnets, but in reality, peering requires non-overlapping CIDRs at the VPC level, and no workaround exists within the peering construct itself.
Detailed technical explanation
How to think about this question
VPC Network Peering uses Google's internal, non-encrypted backbone with sub-millisecond latency and up to 10 Gbps per peering link per region, scaling automatically. Overlapping IP ranges cause routing table conflicts because peering creates static routes for the entire peered CIDR; even with custom route advertisements, the VPC's implicit local route (10.0.0.0/16) takes precedence, blocking traffic. In contrast, HA VPN with dynamic routing can use BGP to advertise more specific prefixes (e.g., /24 subnets) to work around overlaps, but this adds complexity and performance trade-offs.
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 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.
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.
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Re-IP one of the VPC networks to a non-conflicting range and then use VPC Network Peering. — Option A is correct because VPC Network Peering requires non-overlapping IP ranges to establish direct connectivity. By re-IPing one VPC to a non-conflicting range (e.g., 10.1.0.0/16), you eliminate the routing conflict, allowing peering to provide high throughput and low latency via Google's internal backbone, with no bandwidth limits or single points of failure.
What should I do if I get this PCSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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