- A
Create a VPC firewall rule to allow traffic on the VLAN attachment
Why wrong: Firewall rules are not specific to VLAN attachments; they apply to all ingressing traffic equally.
- B
Add a firewall rule in the VPC allowing traffic from the on-premises IP ranges on the interconnect
Why wrong: VPC firewall rules apply to all ingress regardless of connection type, so no additional rule is needed.
- C
Adjust the BGP metric (MED) on the Cloud Router for the Partner Interconnect VLAN attachment to be lower than the VPN route
Without explicitly setting a lower metric, the route from the VPN might be preferred; lowering the metric makes the interconnect the preferred path.
- D
Delete the Cloud VPN tunnel and gateway to force traffic over the interconnect
Why wrong: Deleting the VPN would cause downtime; it's better to first test the interconnect before removing the VPN.
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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.
A company currently uses a site-to-site Cloud VPN (IPsec) to connect their on-premises network to a VPC. Due to growing bandwidth demands, they plan to migrate to Partner Interconnect using a supported service provider. They have ordered a 1 Gbps connection and the provider has indicated the VLAN attachment is ready. After creating the VLAN attachment and pairing it with a Cloud Router, the on-premises router sees the BGP session come up, but no traffic is forwarded over the interconnect. The Cloud VPN is still operational. What step is most likely missing?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Adjust the BGP metric (MED) on the Cloud Router for the Partner Interconnect VLAN attachment to be lower than the VPN route
Option C is correct because when both a Cloud VPN and a Partner Interconnect are connected to the same VPC, the Cloud Router will have multiple BGP routes for the same destination prefixes. By default, the VPN BGP session may have a lower MED (Multi-Exit Discriminator) or a higher local preference, causing traffic to prefer the VPN path. Lowering the MED on the VLAN attachment's BGP session makes the interconnect route more preferred, allowing traffic to be forwarded over the interconnect without deleting the VPN.
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.
- ✗
Create a VPC firewall rule to allow traffic on the VLAN attachment
- ✗
Add a firewall rule in the VPC allowing traffic from the on-premises IP ranges on the interconnect
Why it's wrong here
VPC firewall rules apply to all ingress regardless of connection type, so no additional rule is needed.
- ✓
Adjust the BGP metric (MED) on the Cloud Router for the Partner Interconnect VLAN attachment to be lower than the VPN route
Why this is correct
Without explicitly setting a lower metric, the route from the VPN might be preferred; lowering the metric makes the interconnect the preferred path.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Delete the Cloud VPN tunnel and gateway to force traffic over the interconnect
Why it's wrong here
Deleting the VPN would cause downtime; it's better to first test the interconnect before removing the VPN.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that firewall rules are the missing step for traffic flow over a new interconnect, when in fact the issue is BGP route preference between parallel connections.
Detailed technical explanation
How to think about this question
BGP path selection on Cloud Router uses the standard BGP decision process: highest local preference, shortest AS path, lowest MED, and then IGP cost. By default, Google Cloud assigns a MED of 100 to custom-learned routes from VLAN attachments, while VPN tunnels may have a MED of 0, making the VPN route preferred. Adjusting the MED on the VLAN attachment to a value lower than the VPN's MED (e.g., 50) ensures the interconnect route is chosen. In a real-world scenario, you might also use AS path prepending or local preference manipulation if MED alone is insufficient.
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.
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Implementing hybrid interconnectivity — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
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: Adjust the BGP metric (MED) on the Cloud Router for the Partner Interconnect VLAN attachment to be lower than the VPN route — Option C is correct because when both a Cloud VPN and a Partner Interconnect are connected to the same VPC, the Cloud Router will have multiple BGP routes for the same destination prefixes. By default, the VPN BGP session may have a lower MED (Multi-Exit Discriminator) or a higher local preference, causing traffic to prefer the VPN path. Lowering the MED on the VLAN attachment's BGP session makes the interconnect route more preferred, allowing traffic to be forwarded over the interconnect without deleting the VPN.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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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