- A
Cloud NAT
Required for private instances to reach the internet.
- B
Private Google Access
Why wrong: Allows access to Google APIs privately, not for general external IPs.
- C
Routes with next hop to a firewall instance
Forces traffic through a firewall for inspection and filtering.
- D
Firewall rules on the instance OS
Why wrong: Instance-level firewall rules are not managed by GCP and are outside the scope of VPC network configuration.
- E
VPC firewall rules (egress)
Egress rules control what destinations instances can reach.
Question 943 of 1,000
hardMultiple SelectObjective-mapped
Using Egress Firewall Rules, Cloud NAT, and Routing to Restrict Outbound Traffic
This PCSE practice question tests your understanding of pcse exam topics. 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 security engineer needs to restrict outbound traffic from a VPC to only allow specific external IP ranges. Which three components must be configured? (Choose three.)
Quick Answer
The answer is egress VPC firewall rules, Cloud NAT, and routing through a firewall appliance. To restrict outbound traffic to specific IPs, egress firewall rules define which destination IP ranges are permitted, while Cloud NAT allows instances without public IPs to reach the internet through a managed translation service. However, because VPC firewall rules alone cannot inspect traffic or enforce granular policies like protocol filtering, you must configure custom routes to direct outbound traffic through a firewall appliance, which performs deep packet inspection and enforces the allowed IP list. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of how to combine network-level controls—firewall rules, NAT, and routing—to achieve secure egress, with a common trap being that Cloud NAT alone does not restrict destinations; it only provides connectivity. Remember the mnemonic “FNR” for Firewall, NAT, Routing: without all three, your outbound restriction is incomplete.
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
✓
Cloud NAT
To restrict outbound traffic to specific external IP ranges, you need egress firewall rules (E) to define allowed destinations. If instances have no public IPs, you need Cloud NAT (A) to provide outbound internet access while hiding private IPs. To enforce granular filtering or logging, traffic can be routed through a firewall appliance via custom routes (C). Private Google Access (B) is for reaching Google APIs without public IPs, not for restricting external ranges. Firewall rules on instance OS (D) are not a VPC-level component and are not required for this scenario.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Cloud NAT
Why this is correct
Required for private instances to reach the internet.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Private Google Access
Why it's wrong here
Allows access to Google APIs privately, not for general external IPs.
- ✓
Routes with next hop to a firewall instance
- ✗
Firewall rules on the instance OS
Why it's wrong here
Instance-level firewall rules are not managed by GCP and are outside the scope of VPC network configuration.
- ✓
VPC firewall rules (egress)
Why this is correct
Egress rules control what destinations instances can reach.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCSE NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this PCSE question test?
Static NAT maps one inside address to one outside address.
What is the correct answer to this question?
The correct answer is: Cloud NAT — To restrict outbound traffic to specific external IP ranges, you need egress firewall rules (E) to define allowed destinations. If instances have no public IPs, you need Cloud NAT (A) to provide outbound internet access while hiding private IPs. To enforce granular filtering or logging, traffic can be routed through a firewall appliance via custom routes (C). Private Google Access (B) is for reaching Google APIs without public IPs, not for restricting external ranges. Firewall rules on instance OS (D) are not a VPC-level component and are not required for this scenario.
What should I do if I get this PCSE question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCSE NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
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