- A
Ensure that the firewall rules in the VPC allow traffic from the on-premises IP ranges.
Even with routes, firewall rules must permit the traffic.
- B
Verify that the Cloud Router is using the correct ASN.
Why wrong: If BGP session is established, ASN is correct.
- C
Verify that the on-premises VPN device is advertising the correct networks to Cloud Router.
If on-premises is not advertising its routes, Cloud Router won't have routes to send traffic back.
- D
Check that the Cloud VPN gateway has the correct pre-shared key configured.
Why wrong: If BGP session is up, the tunnel is already established; PSK is fine.
- E
Confirm that the VLAN attachment is of type PARTNER_PROVIDER.
Why wrong: This is irrelevant for VPN; it's for Partner Interconnect.
Question 206 of 1,000
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.
A network engineer is troubleshooting a VPN tunnel that is up but not passing traffic. The Cloud Router shows that BGP sessions are established, but routes are not being exchanged. Which two should the engineer check? (Choose two.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Ensure that the firewall rules in the VPC allow traffic from the on-premises IP ranges.
Common issues: incorrect firewall rules blocking the traffic, or the route advertisements are not configured correctly (e.g., not advertising the correct prefixes).
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Ensure that the firewall rules in the VPC allow traffic from the on-premises IP ranges.
- ✗
Verify that the Cloud Router is using the correct ASN.
Why it's wrong here
If BGP session is established, ASN is correct.
- ✓
Verify that the on-premises VPN device is advertising the correct networks to Cloud Router.
Why this is correct
If on-premises is not advertising its routes, Cloud Router won't have routes to send traffic back.
Related concept
Access ports place end devices into a single VLAN.
- ✗
Check that the Cloud VPN gateway has the correct pre-shared key configured.
Why it's wrong here
If BGP session is up, the tunnel is already established; PSK is fine.
- ✗
Confirm that the VLAN attachment is of type PARTNER_PROVIDER.
Why it's wrong here
This is irrelevant for VPN; it's for Partner Interconnect.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related PCNE questions on switching, trunking, and access-port configuration.
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Implementing Hybrid Interconnectivity — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing Hybrid Interconnectivity — This question tests Implementing Hybrid Interconnectivity — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Ensure that the firewall rules in the VPC allow traffic from the on-premises IP ranges. — Common issues: incorrect firewall rules blocking the traffic, or the route advertisements are not configured correctly (e.g., not advertising the correct prefixes).
What should I do if I get this PCNE question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related PCNE questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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Last reviewed: Jul 4, 2026
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.
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