- A
Use route advertisements from on-prem routers and rely on GCP's route import policy
Correct. Configuring a route import policy (BGP prefix filter) on Cloud Router allows you to accept only specific on-premises prefixes, preventing leaks.
- B
Configure Cloud Router with custom advertised route maps to filter prefixes
Why wrong: Incorrect. Custom advertised route maps on Cloud Router control which prefixes GCP advertises to on-premises, not which prefixes are accepted from on-premises.
- C
Use VPC firewall rules to restrict incoming traffic
Why wrong: Incorrect. VPC firewall rules filter traffic based on IP addresses or ports, but they do not affect BGP routing updates or prefix advertisement acceptance.
- D
Set up a separate Cloud Router for each prefix
Why wrong: Incorrect. Using separate Cloud Routers for each prefix is unnecessary and adds complexity. A single Cloud Router with proper BGP prefix filters can handle multiple prefixes.
PCNE BGP prefix filters Practice Question
This PCNE practice question tests your understanding of bgp prefix filters. 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. A key principle to apply: bGP prefix filters. 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 has a complex on-premises network with multiple BGP AS numbers. They are connecting to GCP using Cloud VPN and wish to advertise specific prefixes. They want to ensure that only selected on-prem prefixes are advertised to GCP and no other prefixes leak. What is the best approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Use route advertisements from on-prem routers and rely on GCP's route import policy
Cloud Router allows you to configure inbound BGP route filtering using route import policies (BGP prefix filters). By applying these filters, you can specify which on-premises prefixes are accepted, ensuring only selected prefixes are learned by GCP. This prevents unwanted prefix leaks and gives you direct control over what enters your VPC from the on-premises network via Cloud VPN. Custom advertised route maps control outbound advertisements from GCP, not inbound filtering.
Key principle: BGP prefix filters
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use route advertisements from on-prem routers and rely on GCP's route import policy
- ✗
Configure Cloud Router with custom advertised route maps to filter prefixes
Why it's wrong here
Incorrect. Custom advertised route maps on Cloud Router control which prefixes GCP advertises to on-premises, not which prefixes are accepted from on-premises.
- ✗
Use VPC firewall rules to restrict incoming traffic
- ✗
Set up a separate Cloud Router for each prefix
Why it's wrong here
Incorrect. Using separate Cloud Routers for each prefix is unnecessary and adds complexity. A single Cloud Router with proper BGP prefix filters can handle multiple prefixes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often confuse outbound and inbound route filtering. Custom advertised route maps filter outbound advertisements from GCP, not inbound prefixes from on-premises. The correct inbound filtering mechanism is Cloud Router's BGP prefix filters (route import policy).
Detailed technical explanation
How to think about this question
Cloud Router uses BGP to exchange routes with on-premises routers over Cloud VPN tunnels. Custom advertised route maps leverage BGP outbound route filtering (ORF) or prefix-list-based filtering to restrict which prefixes are sent in BGP UPDATE messages. This is analogous to using a route-map with match ip address prefix-list on a Cisco router to control outbound advertisements, ensuring strict prefix control.
KKey Concepts to Remember
- BGP prefix filters
- Route import policy
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
BGP prefix filters
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 bGP prefix filters, then practise related PCNE questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this PCNE question test?
BGP prefix filters
What is the correct answer to this question?
The correct answer is: Use route advertisements from on-prem routers and rely on GCP's route import policy — Cloud Router allows you to configure inbound BGP route filtering using route import policies (BGP prefix filters). By applying these filters, you can specify which on-premises prefixes are accepted, ensuring only selected prefixes are learned by GCP. This prevents unwanted prefix leaks and gives you direct control over what enters your VPC from the on-premises network via Cloud VPN. Custom advertised route maps control outbound advertisements from GCP, not inbound filtering.
What should I do if I get this PCNE question wrong?
Review bGP prefix filters, then practise related PCNE questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
BGP prefix filters
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Last reviewed: Jun 25, 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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