The answer is to enable MACsec on the Dedicated Interconnect. This is correct because MACsec (IEEE 802.1AE) provides Layer 2 encryption directly on the interconnect link, securing all traffic between your on-premises router and the Google Cloud edge router without requiring application changes or additional VPN gateways. It minimizes overhead and complexity by operating transparently at the data link layer, adding negligible latency compared to IPsec or TLS. On the Google Professional Cloud Network Engineer exam, this question tests your understanding of when to choose MACsec over IPsec or TLS for dedicated connectivity; a common trap is assuming you must always use a VPN tunnel for encryption, but MACsec is the simpler, lower-overhead solution when you have a Dedicated Interconnect. Remember: MACsec is for the MAC layer—think “MAC on the wire” for direct, low-complexity encryption on dedicated links.
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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 services company is required to encrypt all data in transit between their on-premises data center and Google Cloud. They have a Dedicated Interconnect connection. They want to meet the encryption requirement while minimizing overhead and complexity. Which solution should they implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable MACsec on the Dedicated Interconnect
MACsec (IEEE 802.1AE) provides Layer 2 encryption on the Dedicated Interconnect link itself, encrypting all traffic between the on-premises router and the Google Cloud edge router without requiring any changes to applications or additional VPN gateways. This meets the encryption requirement with minimal overhead and complexity because MACsec operates transparently at the data link layer, adding negligible latency and no per-packet processing overhead compared to IPsec or TLS.
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.
✓
Enable MACsec on the Dedicated Interconnect
Why this is correct
Provides link-layer encryption with minimal overhead.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable TLS encryption on all applications
Why it's wrong here
Not practical for all traffic; does not encrypt at network layer.
✗
Use Cloud VPN over the internet instead of Dedicated Interconnect
Why it's wrong here
Does not use Dedicated Interconnect and may have latency.
✗
Establish an IPsec VPN tunnel over the Dedicated Interconnect
Why it's wrong here
Adds complexity and overhead; MACsec is simpler.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that IPsec VPNs are the only way to encrypt traffic over a dedicated connection, but MACsec is the correct choice when the requirement is to minimize overhead and complexity because it operates at Layer 2 with hardware offload.
Detailed technical explanation
How to think about this question
MACsec uses a pre-shared connectivity association key (CAK) to derive secure association keys (SAKs) via a 4-way handshake (IEEE 802.1X-2010), encrypting each Ethernet frame with AES-128 or AES-256 in GCM mode. On Google Cloud, MACsec is configured on the Cloud Router's BGP peer interface with a pre-shared key, and the on-premises router must support MACsec (e.g., Cisco ASR 1000 or Nexus 9000 series). A real-world scenario where this matters is a financial firm streaming real-time trade data; MACsec ensures wire-speed encryption without the 5-15% throughput loss typical of IPsec VPNs.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
Implementing hybrid interconnectivity — This question tests Implementing hybrid interconnectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable MACsec on the Dedicated Interconnect — MACsec (IEEE 802.1AE) provides Layer 2 encryption on the Dedicated Interconnect link itself, encrypting all traffic between the on-premises router and the Google Cloud edge router without requiring any changes to applications or additional VPN gateways. This meets the encryption requirement with minimal overhead and complexity because MACsec operates transparently at the data link layer, adding negligible latency and no per-packet processing overhead compared to IPsec or TLS.
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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