The answer is applying BGP MED values to influence path selection. This is correct because asymmetric routing in a Partner Interconnect setup occurs when forward traffic from on-premises to Google Cloud uses one connection, but return traffic from Google Cloud takes a different path, often due to default BGP best-path selection. By setting a lower Multi-Exit Discriminator (MED) value on the preferred interconnect link, you effectively tell Google Cloud’s routers to favor that path for return traffic, thereby matching the forward path and resolving the asymmetry. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of BGP path manipulation for hybrid connectivity, specifically how MED controls inbound traffic to an AS. A common trap is confusing MED with Local Preference—remember that MED is a metric sent to a neighbor to influence their outbound path selection, while Local Preference influences your own outbound traffic. Memory tip: MED = “My Exit Decider” for incoming traffic.
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.
A company is using Partner Interconnect to connect to Google Cloud. They notice that traffic from on-premises to GCP takes one path, but return traffic takes a different path, causing asymmetric routing. How can they resolve this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Apply BGP MED values to influence path selection.
B is correct because applying BGP MED (Multi-Exit Discriminator) values allows you to influence the path selection for return traffic from Google Cloud to your on-premises network. By setting a lower MED value on one of the Partner Interconnect connections, you can make Google Cloud prefer that path for return traffic, thereby matching the forward path and resolving asymmetric routing. This is a standard BGP technique for controlling inbound traffic to an AS.
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 the same BGP ASN on both sides.
Why it's wrong here
Same ASN can cause BGP session issues, not fix asymmetry.
✓
Apply BGP MED values to influence path selection.
Why this is correct
MED allows you to indicate the preferred path for inbound traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable asymmetric routing mode on the Cloud Router.
Why it's wrong here
Cloud Router does not have an asymmetric routing mode.
✗
Use different link-local addresses for each session.
Why it's wrong here
Link-local addresses are for BGP peering; they do not affect routing decisions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that BGP ASN configuration or link-local addresses can fix routing asymmetry, when in fact only path-selection attributes like MED or AS path prepending can influence return traffic in a multi-homed BGP setup.
Detailed technical explanation
How to think about this question
BGP MED is an optional transitive attribute used to influence the inbound traffic decision of a neighboring AS. In the context of Partner Interconnect, Google Cloud uses BGP to exchange routes; by setting a lower MED on one of the redundant connections, you make that path more preferred for return traffic. This is particularly useful when you have multiple connections with different bandwidth or latency characteristics, as it allows fine-grained control over traffic flow without changing the AS path.
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.
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: Apply BGP MED values to influence path selection. — B is correct because applying BGP MED (Multi-Exit Discriminator) values allows you to influence the path selection for return traffic from Google Cloud to your on-premises network. By setting a lower MED value on one of the Partner Interconnect connections, you can make Google Cloud prefer that path for return traffic, thereby matching the forward path and resolving asymmetric routing. This is a standard BGP technique for controlling inbound traffic to an AS.
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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