PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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.
An engineer is configuring Dedicated Interconnect between an on-premises data center and Google Cloud. Cloud Router is set up with BGP sessions. The BGP session remains in Idle state. Which of the following is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Cloud Router's BGP IP address is not in the same subnet as the on-premises router's interface.
The BGP session remains in Idle state because the Cloud Router's BGP IP address is not in the same subnet as the on-premises router's interface. For BGP peering over Dedicated Interconnect, the two routers must be directly connected at Layer 3, meaning their BGP peer IP addresses must belong to the same /30 or /31 subnet. If they are in different subnets, the TCP connection for BGP cannot be established, keeping the session in Idle state.
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.
✓
The Cloud Router's BGP IP address is not in the same subnet as the on-premises router's interface.
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The on-premises router is not advertising the Google Cloud VPC subnet routes.
Why it's wrong here
Missing route advertisement would not prevent BGP session from establishing; session can be up without routes.
✗
The interconnect is not configured with redundant links.
Why it's wrong here
Lack of redundancy does not affect BGP session establishment.
✗
The VLAN attachment is not in the same region as the Cloud Router.
Why it's wrong here
Region mismatch would cause attachment failure, not BGP Idle.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse BGP session states with route advertisement issues, assuming missing routes cause Idle state, when in fact Idle state is a Layer 3 connectivity problem, not a routing policy problem.
Detailed technical explanation
How to think about this question
BGP Idle state is the initial state where the router refuses all incoming BGP connections and does not initiate any. The transition to Connect or Active state requires a valid TCP connection to the peer IP address, which depends on Layer 3 reachability. In Dedicated Interconnect, the Cloud Router and on-premises router exchange BGP updates over a VLAN attachment, and the BGP peer IPs must be in the same RFC 1918 subnet (typically a /30) to ensure direct connectivity without intermediate hops.
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: The Cloud Router's BGP IP address is not in the same subnet as the on-premises router's interface. — The BGP session remains in Idle state because the Cloud Router's BGP IP address is not in the same subnet as the on-premises router's interface. For BGP peering over Dedicated Interconnect, the two routers must be directly connected at Layer 3, meaning their BGP peer IP addresses must belong to the same /30 or /31 subnet. If they are in different subnets, the TCP connection for BGP cannot be established, keeping the session in Idle state.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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