The answer is Cloud Interconnect with MACsec, as it is the only solution that provides Layer 2 encryption while allowing the customer to manage encryption keys on-premise and rotate them every 30 days. MACsec, defined by IEEE 802.1AE, encrypts traffic at the data link layer, which means the encryption keys are controlled entirely by the customer’s on-premises key management system rather than by Google Cloud, meeting strict compliance requirements for key sovereignty and rotation schedules. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how MACsec differs from VPN-based encryption—VPNs typically rely on cloud-managed or pre-shared keys that are harder to rotate on a fixed 30-day cycle without complex automation. A common trap is choosing a VPN solution because it also encrypts traffic, but VPNs operate at Layer 3 and often require cloud-side key management, failing the on-premise control requirement. Memory tip: think “MACsec = My Access Control for keys,” reinforcing that the customer keeps the keys on their own premises.
PCNE Practice Question: Designing, planning, and prototyping a GCP network
This PCNE practice question tests your understanding of designing, planning, and prototyping a gcp network. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 financial company requires encrypted traffic between on-premise and GCP. They have strict compliance requiring that encryption keys are managed on-premise and rotated every 30 days. Which connectivity solution should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Cloud Interconnect with MACsec
B is correct because MACsec (IEEE 802.1AE) provides encryption at Layer 2, which is required for Cloud Interconnect to secure traffic between on-premise and GCP. Unlike VPN solutions, MACsec allows the customer to manage encryption keys on-premise and rotate them every 30 days, meeting strict compliance requirements. Cloud Interconnect with MACsec ensures low-latency, high-bandwidth connectivity while keeping key management under the customer's control.
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.
✗
Cloud VPN with certificate-based authentication using on-prem CA
Why it's wrong here
Certificate rotation can meet requirements, but VPN may not provide the bandwidth or low latency of interconnect.
✓
Cloud Interconnect with MACsec
Why this is correct
MACsec provides encryption with customer-managed keys, easily rotated.
Related concept
Read the scenario before looking for a memorised answer.
✗
Cloud VPN with IKEv2 and pre-shared keys
Why it's wrong here
PSK rotation is manual and not aligned with 30-day policy.
✗
Cloud Interconnect with VLAN attachments
Why it's wrong here
No encryption at layer 2.
✗
Partner Interconnect with a service provider that supports MACsec
Why it's wrong here
Key management may not be fully in customer control.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between Layer 2 encryption (MACsec) and Layer 3 encryption (IPsec), and the trap here is that candidates assume Cloud VPN with IKEv2 or certificate-based authentication can satisfy on-premise key management, but GCP manages the IPsec keys, not the customer.
Detailed technical explanation
How to think about this question
MACsec operates at the data link layer (Layer 2) and uses GCM-AES-128 or GCM-AES-256 encryption to protect Ethernet frames. The key management is handled via MKA (MACsec Key Agreement, IEEE 802.1X-2010), which allows the customer to control the Connectivity Association Key (CAK) and rotate it every 30 days using their own key server. In a real-world scenario, this is critical for financial institutions that need to meet PCI-DSS or SOX compliance, where encryption keys must be customer-managed and rotated regularly.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Designing, planning, and prototyping a GCP network — This question tests Designing, planning, and prototyping a GCP network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cloud Interconnect with MACsec — B is correct because MACsec (IEEE 802.1AE) provides encryption at Layer 2, which is required for Cloud Interconnect to secure traffic between on-premise and GCP. Unlike VPN solutions, MACsec allows the customer to manage encryption keys on-premise and rotate them every 30 days, meeting strict compliance requirements. Cloud Interconnect with MACsec ensures low-latency, high-bandwidth connectivity while keeping key management under the customer's control.
What should I do if I get this PCNE 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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