This PCNE practice question tests your understanding of implementing 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.
Which TWO of the following methods can be used to encrypt traffic between VPC networks?
Use of SSL/TLS at the application layer.
SSL/TLS encrypts application data end-to-end.
VPC peering.
Why wrong: VPC peering does not encrypt traffic.
Cloud Interconnect with VLAN attachments.
Why wrong: Cloud Interconnect provides private connectivity but no encryption.
Cloud VPN with IPsec.
IPsec VPN encrypts traffic between VPN gateways.
Cloud NAT.
Why wrong: Cloud NAT does not encrypt traffic.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use of SSL/TLS at the application layer.
Option A is correct because SSL/TLS operates at the application layer (Layer 7) of the OSI model, providing end-to-end encryption for traffic between VPC networks. When applications use HTTPS (HTTP over TLS), the payload is encrypted before leaving the source, ensuring confidentiality even if the underlying network path is untrusted. This method is independent of the underlying network connectivity, making it suitable for encrypting traffic across VPCs connected via any means, including the public internet.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use of SSL/TLS at the application layer.
Why this is correct
SSL/TLS encrypts application data end-to-end.
Related concept
Read the scenario before looking for a memorised answer.
VPC peering.
Why it's wrong here
VPC peering does not encrypt traffic.
Cloud Interconnect with VLAN attachments.
Why it's wrong here
Cloud Interconnect provides private connectivity but no encryption.
Cloud VPN with IPsec.
Cloud NAT.
Why it's wrong here
Cloud NAT does not encrypt traffic.
Common exam traps
Google Cloud often tests the misconception that VPC peering or Cloud Interconnect inherently encrypts traffic, when in fact they only provide private connectivity without encryption, and candidates must remember that encryption requires explicit protocols like IPsec or TLS.
Detailed technical explanation
SSL/TLS encryption relies on a handshake process that negotiates cipher suites, exchanges certificates, and establishes session keys (e.g., using Diffie-Hellman key exchange). In a VPC-to-VPC scenario, applications must be configured to use HTTPS or other TLS-enabled protocols, and the traffic is encrypted end-to-end, meaning even if the underlying network path includes intermediate hops (e.g., through Cloud VPN or the internet), the payload remains confidential. A subtle behavior is that TLS does not protect metadata such as IP headers or DNS queries, which can still be observed by network intermediaries.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Implementing network security — This question tests Implementing network security — Read the scenario before looking for a memorised answer..
The correct answer is: Use of SSL/TLS at the application layer. — Option A is correct because SSL/TLS operates at the application layer (Layer 7) of the OSI model, providing end-to-end encryption for traffic between VPC networks. When applications use HTTPS (HTTP over TLS), the payload is encrypted before leaving the source, ensuring confidentiality even if the underlying network path is untrusted. This method is independent of the underlying network connectivity, making it suitable for encrypting traffic across VPCs connected via any means, including the public internet.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 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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