PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
You are designing a hybrid network using Cloud VPN with dynamic routing (BGP) to connect multiple on-premises sites to Google Cloud. What is a best practice to avoid asymmetric routing when you have multiple VPN tunnels from different on-premises routers?
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 all on-premises routers with the same BGP ASN and enable ECMP on the Cloud Router
Option C is correct because using the same BGP ASN on all on-premises routers and enabling ECMP on the Cloud Router allows the Cloud Router to treat multiple BGP sessions as equal-cost paths. This prevents asymmetric routing by ensuring that return traffic can be load-balanced across any available tunnel, while the same ASN avoids BGP loop-prevention mechanisms that would otherwise reject routes from routers with different ASNs.
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.
✗
Use static routes instead of BGP to have precise control over path selection
Why it's wrong here
Static routes are not dynamic and cannot adapt to failures, also prone to asymmetric routing.
✗
Use a different BGP ASN for each on-premises router to ensure uniqueness
Why it's wrong here
Different ASNs can cause one router's routes to be preferred over others, leading to asymmetry.
✓
Configure all on-premises routers with the same BGP ASN and enable ECMP on the Cloud Router
Why this is correct
Same ASN allows multiple sessions to be treated as redundant, and ECMP load balances traffic.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable ECMP on the Cloud Router to avoid multipath issues
Why it's wrong here
Disabling ECMP reduces redundancy and can cause traffic to stick to one tunnel.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly think different ASNs are required for redundancy, but in fact, using the same ASN is necessary to allow ECMP and avoid BGP loop prevention rejecting routes from multiple on-premises routers.
Detailed technical explanation
How to think about this question
Under the hood, BGP’s loop-prevention mechanism (AS_PATH attribute) discards routes that contain the local ASN. When all on-premises routers share the same ASN, the Cloud Router sees multiple paths with identical AS_PATH lengths, enabling ECMP to install multiple next hops. In a real-world scenario with redundant tunnels across different regions, this design ensures that traffic from an on-premises site can egress via one tunnel and return via another without being dropped, as long as the Cloud Router has ECMP enabled and the same ASN is used.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 all on-premises routers with the same BGP ASN and enable ECMP on the Cloud Router — Option C is correct because using the same BGP ASN on all on-premises routers and enabling ECMP on the Cloud Router allows the Cloud Router to treat multiple BGP sessions as equal-cost paths. This prevents asymmetric routing by ensuring that return traffic can be load-balanced across any available tunnel, while the same ASN avoids BGP loop-prevention mechanisms that would otherwise reject routes from routers with different ASNs.
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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