The correct answer is to create a firewall rule that allows outbound traffic from nodes to 169.254.169.254 only from the internal VPC range (10.0.0.0/8), and deny all other outbound traffic to that IP. This works because the GKE metadata server is a link-local service at 169.254.169.254, and by default any pod or VM can query it; restricting outbound traffic at the node level ensures only workloads originating from the trusted VPC range can reach that sensitive endpoint. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of network-layer metadata protection, often appearing in questions about confidential VMs or multi-tenant clusters where unauthorized pods could exfiltrate service account tokens. A common trap is thinking you need an ingress rule, but the metadata server is a destination, so egress rules on the nodes are required. Memory tip: think “egress to 169.254.169.254” — the metadata server is always a target, never a source.
PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. 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.
A company runs a GKE cluster with multiple node pools, including one pool of confidential VMs. The security team wants to ensure that only traffic from the internal VPC (10.0.0.0/8) can reach the nodes' metadata server. Which configuration should be applied?
Why wrong: Private Google Access allows instances to reach Google APIs without external IPs, not metadata server restriction.
B
Create a firewall rule that allows outbound traffic from nodes to 169.254.169.254 only from the internal VPC range, and deny all other outbound to that IP.
The metadata server IP is 169.254.169.254; firewall rules can restrict outbound access to this IP.
C
Enable IAP TCP forwarding on the cluster.
Why wrong: IAP is for user access to instances, not for restricting metadata server access from nodes.
D
Apply a VPC Service Controls perimeter to the GKE cluster.
Why wrong: VPC Service Controls protect Google-managed services, not compute instance metadata.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a firewall rule that allows outbound traffic from nodes to 169.254.169.254 only from the internal VPC range, and deny all other outbound to that IP.
The metadata server for GKE nodes is accessible at the link-local IP 169.254.169.254. To restrict access to this server to traffic originating only from the internal VPC range (10.0.0.0/8), you must create a firewall rule that allows outbound traffic from the nodes to 169.254.169.254 only from that range, and then deny all other outbound traffic to that IP. This ensures that only workloads within the internal VPC can query instance metadata, preventing external or unauthorized pods from accessing sensitive metadata.
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.
✗
Configure Private Google Access on the subnets.
Why it's wrong here
Private Google Access allows instances to reach Google APIs without external IPs, not metadata server restriction.
✓
Create a firewall rule that allows outbound traffic from nodes to 169.254.169.254 only from the internal VPC range, and deny all other outbound to that IP.
Why this is correct
The metadata server IP is 169.254.169.254; firewall rules can restrict outbound access to this IP.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable IAP TCP forwarding on the cluster.
Why it's wrong here
IAP is for user access to instances, not for restricting metadata server access from nodes.
✗
Apply a VPC Service Controls perimeter to the GKE cluster.
Why it's wrong here
VPC Service Controls protect Google-managed services, not compute instance metadata.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Private Google Access or VPC Service Controls can restrict metadata server access, but the metadata server is a link-local service that must be controlled via egress firewall rules targeting the specific IP 169.254.169.254.
Detailed technical explanation
How to think about this question
The metadata server at 169.254.169.254 is a link-local address (169.254.0.0/16) that is not routable across subnets or VPCs; traffic to it is handled by the local network stack. Firewall rules in GCP are stateful, so an egress deny rule for 169.254.169.254 will block all outbound connections to that IP unless an allow rule with a higher priority explicitly permits traffic from the internal VPC range. In practice, this configuration is critical for confidential VMs where metadata may contain sensitive data like service account tokens or startup scripts.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a firewall rule that allows outbound traffic from nodes to 169.254.169.254 only from the internal VPC range, and deny all other outbound to that IP. — The metadata server for GKE nodes is accessible at the link-local IP 169.254.169.254. To restrict access to this server to traffic originating only from the internal VPC range (10.0.0.0/8), you must create a firewall rule that allows outbound traffic from the nodes to 169.254.169.254 only from that range, and then deny all other outbound traffic to that IP. This ensures that only workloads within the internal VPC can query instance metadata, preventing external or unauthorized pods from accessing sensitive metadata.
What should I do if I get this PCSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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