The answer is that the Cloud Router is not configured to accept BGP connections from this on-premises peer. When an on-premises router receives a 'Connection refused' error, it means the TCP handshake for the BGP session was actively rejected at the transport layer, which points directly to a missing or inactive peer configuration on the Cloud Router side. This is a classic scenario on the Google Professional Cloud Network Engineer exam, testing your ability to distinguish between tunnel-level issues and BGP session misconfigurations—a common trap is assuming the VPN tunnel itself is the problem when it may be up and running. The key insight is that a Cloud VPN tunnel can be established without a BGP session, so the refusal indicates the Cloud Router has no peer definition for that specific on-premises IP. Memory tip: think of the Cloud Router as a bouncer—if the peer’s IP isn’t on the list, the TCP connection gets refused at the door.
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.
Exhibit
Refer to the exhibit.
Output from an on-premises router:
```
show bgp vpnv4 unicast neighbors 169.254.1.1
BGP neighbor is 169.254.1.1, vrf default
BGP version 4, remote router ID 10.0.0.1
BGP state = Connect
Last read never, last write never
Hold time is 90, keepalive interval is 30 seconds
No using MD5 authentication
Error: Connection refused
```
Refer to the exhibit. A Cloud VPN tunnel is configured between an on-premises router and Google Cloud. The BGP session is not established. The on-premises router shows 'Connection refused'. 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.
Refer to the exhibit.
Output from an on-premises router:
```
show bgp vpnv4 unicast neighbors 169.254.1.1
BGP neighbor is 169.254.1.1, vrf default
BGP version 4, remote router ID 10.0.0.1
BGP state = Connect
Last read never, last write never
Hold time is 90, keepalive interval is 30 seconds
No using MD5 authentication
Error: Connection refused
```
A
The Cloud VPN tunnel is not established.
Why wrong: If the tunnel were down, the error would be 'Network unreachable' or 'No route to host', not 'Connection refused'.
B
The on-premises router's BGP configuration has the wrong ASN.
Why wrong: ASN mismatch would cause BGP to send an OPEN message error after TCP connects, not a TCP connection refusal.
C
The BGP MD5 password is mismatched between the two peers.
Why wrong: MD5 authentication mismatch would cause a BGP NOTIFICATION, not a TCP connection refusal.
D
The Cloud Router is not configured to accept BGP connections from this on-premises peer.
'Connection refused' indicates the Cloud Router TCP port 179 is not accepting the connection, likely because the BGP peer is not defined on the Cloud Router or the interface is down.
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 is not configured to accept BGP connections from this on-premises peer.
The 'Connection refused' error on the on-premises router indicates that the Cloud Router is actively rejecting the TCP connection attempt for the BGP session. This typically occurs when the Cloud Router does not have a BGP peer configured with the on-premises router's IP address, or the peer is in an 'inactive' state. Since the Cloud VPN tunnel itself can be established (option A is not necessarily true), the most likely cause is that the Cloud Router is not configured to accept BGP connections from this specific on-premises peer.
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 VPN tunnel is not established.
Why it's wrong here
If the tunnel were down, the error would be 'Network unreachable' or 'No route to host', not 'Connection refused'.
✗
The on-premises router's BGP configuration has the wrong ASN.
Why it's wrong here
ASN mismatch would cause BGP to send an OPEN message error after TCP connects, not a TCP connection refusal.
✗
The BGP MD5 password is mismatched between the two peers.
Why it's wrong here
MD5 authentication mismatch would cause a BGP NOTIFICATION, not a TCP connection refusal.
✓
The Cloud Router is not configured to accept BGP connections from this on-premises peer.
Why this is correct
'Connection refused' indicates the Cloud Router TCP port 179 is not accepting the connection, likely because the BGP peer is not defined on the Cloud Router or the interface is down.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between TCP-level errors (like 'Connection refused') and BGP-level errors (like ASN mismatch or MD5 failure), leading candidates to incorrectly choose B or C when they see a BGP-related symptom without analyzing the specific error message.
Detailed technical explanation
How to think about this question
When a BGP session is initiated, the TCP three-way handshake must succeed before any BGP messages are exchanged. A 'Connection refused' error is a TCP RST (reset) sent by the receiving host, indicating that no process is listening on the destination port (TCP 179). In Google Cloud, Cloud Router acts as the BGP listener; if the peer IP is not explicitly configured in the BGP peer list, the Cloud Router's TCP stack will reject the connection attempt. This is different from a firewall block, which would typically result in a timeout or ICMP unreachable, not a TCP RST.
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: The Cloud Router is not configured to accept BGP connections from this on-premises peer. — The 'Connection refused' error on the on-premises router indicates that the Cloud Router is actively rejecting the TCP connection attempt for the BGP session. This typically occurs when the Cloud Router does not have a BGP peer configured with the on-premises router's IP address, or the peer is in an 'inactive' state. Since the Cloud VPN tunnel itself can be established (option A is not necessarily true), the most likely cause is that the Cloud Router is not configured to accept BGP connections from this specific on-premises peer.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This PCNE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNE exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.