PCNE Configuring Network Services Practice Question
A company has an on-premises data center connected to GCP via Cloud VPN with dynamic routing (BGP). Recently, connectivity to a specific subnet (10.1.0.0/16) in GCP became intermittent. The VPN tunnel is up, and BGP sessions are established. What is the most likely cause?
⚠ Common exam trap
Google Cloud often tests the misconception that if the VPN tunnel and BGP session are up, all subnets must be reachable, but the trap is that route advertisement misconfiguration can cause selective subnet unreachability even when the control plane is healthy.
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
✓
The Cloud Router is not advertising the correct subnet range to the on-premises router.
Since the VPN tunnel is up and BGP sessions are established, the issue is not with the tunnel or BGP peering itself. Intermittent connectivity to a specific subnet (10.1.0.0/16) while other subnets remain reachable strongly indicates a route advertisement problem. The Cloud Router must be configured to advertise the correct subnet range to the on-premises router via BGP; if it is not, the on-premises router will lack a route for that subnet, causing intermittent or no connectivity.
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 shared secret is misconfigured.
Why it's wrong here
Wrong shared secret would prevent tunnel establishment.
- ✗
The VPN tunnel is flapping due to packet loss.
Why it's wrong here
Tunnel stability is unrelated to intermittent connectivity to a specific subnet.
- ✗
A firewall rule is blocking traffic from on-premises.
Why it's wrong here
Firewall rules control allowed traffic, not routing.
- ✓
The Cloud Router is not advertising the correct subnet range to the on-premises router.
Why this is correct
If the subnet is not advertised, on-premises traffic may not be routed correctly.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.