The answer is to use the same private ASN for all Cloud Routers in the same region. This is correct because when configuring BGP ASN for multiple tunnels in a Global Cloud VPN, the on-premises BGP speaker treats all tunnels from that region as a single BGP session, enabling ECMP load balancing and seamless failover without introducing AS path prepending or path selection conflicts. On the Google Professional Cloud Network Engineer exam, this concept tests your understanding of how Cloud Router redundancy interacts with on-premises peer configuration—a common trap is assuming each Cloud Router needs a unique ASN, which would cause the on-premises router to see multiple distinct peers and break optimal routing. The key insight is that Google Cloud recommends identical private ASNs per region to simplify routing policy and avoid unnecessary BGP updates. Memory tip: think “Same ASN, Same Region” for stable multi-tunnel peering.
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 company is deploying a Global Cloud VPN with multiple tunnels from different Cloud Router instances to the same on-premises peer. The on-premises BGP speaker is configured with multiple peers. How should they configure the BGP ASN on the Cloud Routers to ensure optimal routing?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the same private ASN for all Cloud Routers in the same region.
Option B is correct because using the same private ASN on all Cloud Routers in the same region allows the on-premises BGP speaker to treat multiple tunnels from that region as a single BGP session, enabling load balancing and failover without creating BGP path selection issues. This approach aligns with Google Cloud's recommendation for redundant VPN tunnels, where the same ASN ensures the on-premises router sees the Cloud Routers as a single BGP peer, simplifying routing policy and avoiding unnecessary AS path prepending.
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 different private ASNs for each Cloud Router to differentiate the tunnels.
Why it's wrong here
Different ASNs would cause the on-premises router to see multiple AS paths and may cause routing loops or suboptimal routing.
✓
Use the same private ASN for all Cloud Routers in the same region.
Why this is correct
Same private ASN ensures the on-premises router treats all Cloud Router peers from the same region as one entity, preventing loops and allowing ECMP.
Related concept
Read the scenario before looking for a memorised answer.
✗
Assign a unique public ASN to each Cloud Router.
Why it's wrong here
Public ASNs are not necessary for Cloud VPN and may conflict with on-premises ASN.
✗
Use the same ASN across all Cloud Routers globally.
Why it's wrong here
Using the same ASN globally is not required; it is only recommended within a region for redundancy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume each BGP session needs a unique ASN for redundancy, but in Google Cloud's multi-tunnel VPN design, using the same ASN within a region is required to enable proper load balancing and failover without causing BGP path selection conflicts.
Detailed technical explanation
How to think about this question
In Google Cloud, Cloud Router uses BGP to exchange routes with on-premises routers over VPN tunnels. When multiple Cloud Routers in the same region use the same private ASN, the on-premises BGP speaker sees them as a single BGP peer, allowing it to install multiple equal-cost paths (ECMP) for load balancing. This behavior leverages BGP's ability to accept multiple paths from the same ASN, as defined in RFC 4271, and avoids issues like BGP loop detection or AS path prepending that could degrade routing efficiency.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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: Use the same private ASN for all Cloud Routers in the same region. — Option B is correct because using the same private ASN on all Cloud Routers in the same region allows the on-premises BGP speaker to treat multiple tunnels from that region as a single BGP session, enabling load balancing and failover without creating BGP path selection issues. This approach aligns with Google Cloud's recommendation for redundant VPN tunnels, where the same ASN ensures the on-premises router sees the Cloud Routers as a single BGP peer, simplifying routing policy and avoiding unnecessary AS path prepending.
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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