The correct answer is to configure two BGP sessions, each on a separate Dedicated Interconnect link, with different ASNs and MED values to influence path selection. This approach treats each connection as an independent routing peer, allowing you to use Multi-Exit Discriminator (MED) attributes to steer inbound traffic toward the preferred link while maintaining automatic failover if one connection drops. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how to achieve high availability and traffic engineering without relying on ECMP, which would distribute traffic indiscriminately across both links. A common trap is assuming a single BGP session with multiple links or using the same ASN on both sessions, which prevents MED-based control and can cause routing loops. Remember the memory tip: “Different ASN, separate MED — control the path, not just the speed.”
PCNE Practice Question: Designing, planning, and prototyping a GCP network
This PCNE practice question tests your understanding of designing, planning, and prototyping a gcp network. 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 is planning to migrate their on-premises application to Google Cloud. The application requires consistent high bandwidth and low latency to on-premises databases. They have a Dedicated Interconnect connection with a 10 Gbps link. To improve availability, they decide to add a second Interconnect connection. Which of the following is a best practice for configuring BGP sessions?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure two BGP sessions, each on a separate connection, with different ASNs and MED values to influence path selection
Option B is correct because using different ASNs on each BGP session allows the on-premises router to treat the two Dedicated Interconnect connections as separate routing peers, enabling path selection control via MED values. This ensures that if one connection fails, traffic can be rerouted through the other, improving availability without relying on ECMP or a single session, which would not provide the desired redundancy and traffic engineering.
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 two BGP sessions with the same ASN and MED values
Why it's wrong here
Same ASN and MED values may cause suboptimal routing and potential loops.
✓
Configure two BGP sessions, each on a separate connection, with different ASNs and MED values to influence path selection
Why this is correct
Separate sessions with different ASNs and MED values allow for load balancing and failover.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable ECMP across the two connections with a single BGP session
Why it's wrong here
ECMP requires multiple BGP sessions to advertise the same routes; a single session cannot provide ECMP.
✗
Use a single BGP session across both connections
Why it's wrong here
A single session does not utilize both links for load balancing and creates a single point of failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that a single BGP session can be used across multiple physical connections, but in Google Cloud, each Dedicated Interconnect link requires its own BGP session, and using different ASNs is a best practice for path selection and redundancy.
Detailed technical explanation
How to think about this question
When configuring BGP over Dedicated Interconnect, each connection typically uses a separate BGP session with a unique ASN (often private ASNs like 64512-65534) to allow the on-premises router to distinguish between the two paths. MED values can then be set to influence inbound traffic, while outbound traffic is controlled by local preference or AS path prepending. In a real-world scenario, if one connection experiences degradation, the BGP session can be gracefully terminated, and the remaining session carries all traffic, ensuring high availability without relying on Layer 2 redundancy mechanisms.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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.
Designing, planning, and prototyping a GCP network — This question tests Designing, planning, and prototyping a GCP network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure two BGP sessions, each on a separate connection, with different ASNs and MED values to influence path selection — Option B is correct because using different ASNs on each BGP session allows the on-premises router to treat the two Dedicated Interconnect connections as separate routing peers, enabling path selection control via MED values. This ensures that if one connection fails, traffic can be rerouted through the other, improving availability without relying on ECMP or a single session, which would not provide the desired redundancy and traffic engineering.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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