- A
Set a higher local preference on the west coast Cloud Router for routes received from the east coast data center.
Why wrong: Local preference affects route selection for outbound traffic from GCP to on-premises; but it is applied on the Cloud Router, not on the on-premises side. This would work, but the question asks for on-premises data center collaboration.
- B
Set a higher MED on the west coast data center's BGP advertisements to increase its desirability.
Why wrong: Higher MED makes a path less preferred, so this would deprefer west coast, which could be a solution, but it is static and doesn't adapt to load.
- C
Configure the east coast data center to prepend one additional AS path hop to its advertised routes.
Why wrong: This would make east coast routes less preferred, not more.
- D
Use BGP communities to tag routes from the west coast data center under load, and configure Cloud Router to match these communities and adjust the route priority (MED) accordingly.
This allows dynamic adjustment: when the west coast is loaded, it tags routes with a community, and Cloud Router increases MED for those routes, making east coast more preferred.
Quick Answer
The answer is to use BGP communities for traffic engineering, specifically tagging routes from the overloaded west coast data center and configuring Cloud Router to match those tags and adjust the MED. This works because BGP communities act as metadata tags on route advertisements, allowing the on-premises router to signal its load status dynamically. When Cloud Router receives a route tagged with a community indicating high load, it can lower the MED for that path, making the east coast route more preferred by Google Cloud’s best-path selection algorithm. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of BGP path manipulation without static prefix filtering—a common trap is trying to use AS-path prepending or local preference on the on-premises side, which is less flexible. The key insight is that communities enable policy-based, automated traffic engineering across hybrid networks. Memory tip: think of communities as “BGP stickers” that let on-premises routers tell Cloud Router, “I’m busy, pick the other path.”
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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 large enterprise has multiple on-premises data centers connected to Google Cloud via a combination of Dedicated Interconnect and Cloud VPN. They have a VPC with subnets in us-east1 and us-west1. The on-premises network advertises a prefix 10.0.0.0/8 to both Cloud Routers (each in different regions) via BGP. The Cloud Routers are configured with 'global' dynamic routing mode. The network team notices that traffic from Google Cloud instances in us-west1 to on-premises destinations in 10.0.0.0/8 is always taking the path to the closest on-premises data center (west coast) even though the west coast data center is currently under high load, causing performance degradation. The east coast data center is underutilized. They want to influence the path selection so that the west coast instances prefer the east coast data center during peak times. They are using BGP. What is the most effective method to achieve this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"always"Why it matters: Absolute qualifier. An answer using 'always' is only correct if there are genuinely no exceptions — absolute statements are often wrong in networking.
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
Use BGP communities to tag routes from the west coast data center under load, and configure Cloud Router to match these communities and adjust the route priority (MED) accordingly.
Option D is correct because BGP communities allow the west coast data center to tag its routes with a community value indicating high load. The Cloud Router can then be configured to match this community and adjust the route priority by lowering the MED (or local preference) for those routes, making the east coast data center's routes more preferred. This dynamic, policy-based approach directly addresses the need to shift traffic away from the overloaded west coast data center without manual reconfiguration.
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.
- ✗
Set a higher local preference on the west coast Cloud Router for routes received from the east coast data center.
Why it's wrong here
Local preference affects route selection for outbound traffic from GCP to on-premises; but it is applied on the Cloud Router, not on the on-premises side. This would work, but the question asks for on-premises data center collaboration.
- ✗
Set a higher MED on the west coast data center's BGP advertisements to increase its desirability.
Why it's wrong here
Higher MED makes a path less preferred, so this would deprefer west coast, which could be a solution, but it is static and doesn't adapt to load.
- ✗
Configure the east coast data center to prepend one additional AS path hop to its advertised routes.
Why it's wrong here
This would make east coast routes less preferred, not more.
- ✓
Use BGP communities to tag routes from the west coast data center under load, and configure Cloud Router to match these communities and adjust the route priority (MED) accordingly.
Why this is correct
This allows dynamic adjustment: when the west coast is loaded, it tags routes with a community, and Cloud Router increases MED for those routes, making east coast more preferred.
Clue confirmation
The clue word "always" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse MED and local preference, thinking MED influences outbound path selection from the local AS, when in fact MED is used to influence inbound traffic from a neighboring AS, while local preference is used for outbound path selection within the AS.
Detailed technical explanation
How to think about this question
BGP communities are transitive optional attributes that allow tagging routes with policy information (e.g., 100:100 for 'high load'). Cloud Router can match these communities using route policies (similar to route-maps in Cisco IOS) to adjust the MED value, which is a 4-byte metric that influences the best-path selection when multiple paths to the same prefix are received from the same neighbor AS. In this scenario, the west coast Cloud Router receives two paths for 10.0.0.0/8: one from the west coast data center (with community tag indicating high load) and one from the east coast data center (without the tag). By lowering the MED on the tagged route, the west coast Cloud Router prefers the east coast path, effectively steering traffic away from the overloaded data center. This approach is dynamic and can be automated based on real-time load metrics.
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: Use BGP communities to tag routes from the west coast data center under load, and configure Cloud Router to match these communities and adjust the route priority (MED) accordingly. — Option D is correct because BGP communities allow the west coast data center to tag its routes with a community value indicating high load. The Cloud Router can then be configured to match this community and adjust the route priority by lowering the MED (or local preference) for those routes, making the east coast data center's routes more preferred. This dynamic, policy-based approach directly addresses the need to shift traffic away from the overloaded west coast data center without manual reconfiguration.
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: "always". Absolute qualifier. An answer using 'always' is only correct if there are genuinely no exceptions — absolute statements are often wrong in networking.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 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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