The answer is to use Cloud Router with BGP to exchange specific on-premises prefixes while keeping the default internet route intact. This configuration works because BGP dynamically advertises only the specific routes from your on-premises network into the VPC, so Cloud VPN route selection directs traffic for those learned prefixes through the tunnels, while the default 0.0.0.0/0 route remains pointed at the internet gateway for all other traffic. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how BGP route exchange interacts with VPC routing priority—specifically that more specific routes (e.g., /24) override the default route only for their destination. A common trap is assuming you must remove the default route, which would break internet access; instead, BGP’s dynamic learning gives you precise control without overriding the default. Memory tip: think “BGP for the specific, default for the rest.”
PCNE Configuring network services Practice Question
This PCNE practice question tests your understanding of configuring network services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 has a VPC with multiple subnets and uses Cloud VPN tunnels to connect to on-premises. They want to ensure that only traffic destined for on-premises is sent through the VPN tunnels; all other traffic should use the internet. Which route configuration 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
✓
Use Cloud Router with BGP to exchange specific routes with on-premises, and keep the default internet route for other traffic.
Option B is correct because using Cloud Router with BGP allows the VPC to dynamically learn specific routes from the on-premises network via the VPN tunnels. The default route (0.0.0.0/0) remains pointing to the internet gateway, so only traffic destined for the learned on-premises prefixes is sent through the VPN, while all other traffic uses the internet. This provides precise control without overriding the default route.
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.
✗
Add a static route for 0.0.0.0/0 with next hop VPN gateway, and set a lower priority than the internet default route.
Use Cloud Router with BGP to exchange specific routes with on-premises, and keep the default internet route for other traffic.
Why this is correct
BGP-learned specific routes will override the default route for those destinations.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the Cloud VPN to advertise a default route to on-premises, and rely on local preference.
Why it's wrong here
That would send on-premises traffic to Google, opposite direction.
✗
Use VPC Network Peering with the on-premises network and configure custom route exchange.
Why it's wrong here
Peering is for VPC-to-VPC, not for on-premises.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that a default route (0.0.0.0/0) must be manipulated to direct traffic to on-premises, when in fact the correct approach is to use more specific routes learned via BGP to selectively direct only on-premises-destined traffic through the VPN.
Detailed technical explanation
How to think about this question
Cloud Router uses BGP to exchange routes with on-premises routers over the VPN tunnels. The learned routes are installed in the VPC route table with a next hop of the VPN gateway, and their priority is determined by the route type (static vs. dynamic) and the specific prefix length. By default, more specific routes (e.g., 10.0.0.0/8) take precedence over the less specific default route (0.0.0.0/0), ensuring only traffic matching the learned prefixes goes through the VPN. This is similar to how BGP-based VPNs work in hybrid cloud architectures, where route propagation must be carefully managed to avoid asymmetric routing or blackholing.
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 services — This question tests Configuring network services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Cloud Router with BGP to exchange specific routes with on-premises, and keep the default internet route for other traffic. — Option B is correct because using Cloud Router with BGP allows the VPC to dynamically learn specific routes from the on-premises network via the VPN tunnels. The default route (0.0.0.0/0) remains pointing to the internet gateway, so only traffic destined for the learned on-premises prefixes is sent through the VPN, while all other traffic uses the internet. This provides precise control without overriding the default route.
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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