Question 494 of 961
PCNE Implementing network security Practice Question
A network engineer is troubleshooting connectivity from an on-premises network to a GCE VM through a VPN tunnel. The tunnel is established, but traffic is not reaching the VM. What should the engineer check first?
⚠ Common exam trap
Google Cloud often tests the misconception that a working tunnel implies all traffic flows, but the trap here is that VPC firewall rules are independent of tunnel status and must be explicitly configured for the on-premises subnet as the source.
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
✓
Check VPC firewall rules to ensure ingress traffic from the on-premises subnet is allowed to the VM
VPC firewall rules are the first line of defense for controlling traffic to GCE VMs. Even though the VPN tunnel is established, the default-deny ingress posture of GCP means that traffic from the on-premises subnet must be explicitly allowed by a VPC firewall rule. Without this rule, packets arriving via the tunnel are dropped before they ever reach the VM's network interface.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check VPC firewall rules to ensure ingress traffic from the on-premises subnet is allowed to the VM
Why this is correct
Firewall rules must allow traffic from the on-premises IP range to the VM's target tags or service account.
- ✗
Check the VM's OS firewall to see if it is blocking incoming traffic
Why it's wrong here
The VM’s OS firewall operates at the host level, filtering traffic after it has already been decapsulated from the VPN tunnel and routed to the VM’s network interface. Since the tunnel is established but traffic fails to reach the VM, the issue likely lies in the cloud routing path—such as misconfigured GCP VPC firewall rules, incorrect static routes, or a missing dynamic route advertisement—which prevents packets from even arriving at the VM’s OS. This option is tempting because OS firewalls are a common cause of inbound traffic blocks in on-premises environments, and it would be the correct first check if the tunnel were confirmed to deliver packets to the VM’s internal IP but the application still did not respond.
- ✗
Verify that the VPN tunnel is using the correct pre-shared key
Why it's wrong here
If the tunnel is established, the PSK is correct.
- ✗
Review Cloud Armor security policies that may be blocking the traffic
Why it's wrong here
Cloud Armor applies to load-balanced traffic, not direct VPN traffic.
Visual reference
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 →
Last reviewed: Jun 30, 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.
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.