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.
You are troubleshooting an HA VPN connection between Google Cloud and on-premises. The tunnels appear as 'UP' but no routes are exchanged. The Cloud Router logs show 'BGP session state: IDLE'. What 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
✓
BGP is not enabled on the Cloud Router
B is correct because the BGP session state IDLE indicates that BGP is not configured or enabled on the Cloud Router. Even though the IPsec tunnels are UP, no BGP routes can be exchanged if the BGP process itself is not running. In Google Cloud, you must explicitly enable BGP on the Cloud Router for each VPN tunnel; otherwise, the BGP session cannot transition from IDLE to any other 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 BGP keepalive timer is set too high on the on-premises router
Why it's wrong here
High keepalive may cause delay but session would be ESTABLISHED initially.
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Firewall rules are blocking UDP port 179
Why it's wrong here
If blocked, session would be ACTIVE, not IDLE.
✗
The on-premises BGP peer is configured with a different next-hop IP
Why it's wrong here
Next-hop mismatch affects route processing, not session state.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that a BGP session stuck in IDLE is always a firewall or reachability issue, but in Google Cloud HA VPN, the most common cause is that BGP was never enabled on the Cloud Router, especially when the IPsec tunnels are UP and the candidate assumes BGP is automatically active.
Detailed technical explanation
How to think about this question
The BGP finite state machine defines IDLE as the initial state where BGP is not active—typically because the BGP process is disabled, the neighbor is not configured, or there is a failure in the TCP transport (e.g., no route to the peer). In Google Cloud, Cloud Router BGP sessions require explicit configuration under the router interface for each VPN tunnel; if omitted, the BGP process never starts, leaving the state stuck at IDLE. This differs from on-premises routers where BGP might be enabled globally but a neighbor statement is missing—here the entire BGP process is absent.
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: BGP is not enabled on the Cloud Router — B is correct because the BGP session state IDLE indicates that BGP is not configured or enabled on the Cloud Router. Even though the IPsec tunnels are UP, no BGP routes can be exchanged if the BGP process itself is not running. In Google Cloud, you must explicitly enable BGP on the Cloud Router for each VPN tunnel; otherwise, the BGP session cannot transition from IDLE to any other 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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