The answer is to configure BGP on Cloud Router and advertise custom routes with appropriate metrics. This is correct because BGP allows you to control active/passive failover for Cloud VPN by assigning different Multi-Exit Discriminator (MED) values to primary and backup paths; the lower metric route is preferred while the BGP session is active, and if the session fails, the route is withdrawn and traffic automatically shifts to the higher-metric backup. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of dynamic routing with BGP metrics to achieve path selection without manual intervention, often appearing as a trap where candidates mistakenly choose static routes or VPN tunnels without BGP. Remember the key insight: BGP metrics enable automatic failover by treating the primary path as active and the backup as passive, so think “lower MED wins, session down = route gone.” A useful mnemonic is “MED for MEDical failover: lower number keeps the patient on the primary, higher number is the backup stretcher.”
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 wants to connect their VPC to an on-premises network using Cloud VPN. They need to ensure that traffic from Google Cloud to on-premises uses a specific route only when the primary path is available, and otherwise fails over to a backup path. Which configuration should they use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure BGP on Cloud Router and advertise custom routes with appropriate metrics
Option B is correct because Cloud VPN with dynamic routing (BGP) allows you to control path selection by advertising custom routes with different metrics (MED values) for the primary and backup paths. When the primary path is available, the lower metric route is preferred; if the BGP session fails, the route is withdrawn and traffic automatically fails over to the backup path with a higher metric. This meets the requirement for active/passive failover without manual intervention.
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.
✗
Configure Cloud NAT to route traffic through the backup path
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse static route priority with dynamic BGPmetric-based failover, assuming that a higher-priority static route will automatically fail over when the tunnel is down, but Google Cloud static routes do not have health-check awareness and will continue to forward traffic into a dead tunnel unless the route is removed.
Detailed technical explanation
How to think about this question
In Google Cloud, Cloud Router uses BGP to exchange routes with on-premises routers; by setting a lower MED (Multi-Exit Discriminator) on the primary path, the on-premises router prefers that path. If the BGP session goes down (e.g., tunnel failure), the route is withdrawn, and the backup path (with higher MED) becomes active. This is analogous to RFC 4271 BGP path selection, where MED is compared only when paths come from the same AS. A real-world scenario is a multi-region VPN deployment where primary and backup tunnels terminate in different regions for geographic redundancy.
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.
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: Configure BGP on Cloud Router and advertise custom routes with appropriate metrics — Option B is correct because Cloud VPN with dynamic routing (BGP) allows you to control path selection by advertising custom routes with different metrics (MED values) for the primary and backup paths. When the primary path is available, the lower metric route is preferred; if the BGP session fails, the route is withdrawn and traffic automatically fails over to the backup path with a higher metric. This meets the requirement for active/passive failover without manual intervention.
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.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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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