- A
Set up a VPC peering connection
Why wrong: VPC peering is for connecting VPCs, not for advertising subnets via VPN.
- B
Use static routes on the VPN tunnel
Why wrong: Static routes bypass BGP; they do not allow dynamic advertisement of VPC subnets.
- C
Create a custom route advertisement for each subnet
Cloud Router can be configured with custom route advertisements to advertise specific VPC subnets to the on-premises network via BGP.
- D
Configure the VPN gateway to advertise the subnets
Why wrong: The VPN gateway does not handle BGP advertisements; Cloud Router does.
Question 583 of 982
PCNE Implementing Hybrid Interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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.
An engineer is configuring a Cloud Router for HA VPN. They need to enable BGP on the VPN tunnels. Which BGP configuration is required for the Cloud Router to advertise the VPC subnets to the on-premises network?
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
✓
Create a custom route advertisement for each subnet
Option C is correct because Cloud Router uses Border Gateway Protocol (BGP) to dynamically exchange routes with the on-premises network over HA VPN tunnels. By default, Cloud Router advertises only the VPC subnet ranges that are directly connected to the VPC network. To ensure all VPC subnets are advertised, you must create custom route advertisements for each subnet that needs to be reachable from on-premises. This is done by configuring the Cloud Router with a custom advertisement mode and specifying the subnet CIDR ranges as custom advertised IP ranges.
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.
- ✗
Set up a VPC peering connection
Why it's wrong here
VPC peering is for connecting VPCs, not for advertising subnets via VPN.
- ✗
Use static routes on the VPN tunnel
Why it's wrong here
Static routes bypass BGP; they do not allow dynamic advertisement of VPC subnets.
- ✓
Create a custom route advertisement for each subnet
Why this is correct
Cloud Router can be configured with custom route advertisements to advertise specific VPC subnets to the on-premises network via BGP.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure the VPN gateway to advertise the subnets
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the VPN gateway itself handles BGP route advertisements, when in fact it is the Cloud Router that acts as the BGP speaker and manages route exchange for HA VPN tunnels.
Detailed technical explanation
How to think about this question
Cloud Router implements BGP-4 (RFC 4271) and supports both global and regional dynamic routing modes. When using custom route advertisements, you can also advertise specific routes (e.g., /32 host routes) or even non-VPC routes, which is useful in scenarios where you need to advertise a default route or a summarized prefix to on-premises. A subtle behavior is that Cloud Router will not automatically advertise subnets from a different region unless you explicitly add them as custom advertisements, which is a common pitfall in multi-region VPC designs.
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 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.
Visual reference
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing Hybrid Interconnectivity — This question tests Implementing Hybrid Interconnectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a custom route advertisement for each subnet — Option C is correct because Cloud Router uses Border Gateway Protocol (BGP) to dynamically exchange routes with the on-premises network over HA VPN tunnels. By default, Cloud Router advertises only the VPC subnet ranges that are directly connected to the VPC network. To ensure all VPC subnets are advertised, you must create custom route advertisements for each subnet that needs to be reachable from on-premises. This is done by configuring the Cloud Router with a custom advertisement mode and specifying the subnet CIDR ranges as custom advertised IP ranges.
What should I do if I get this PCNE 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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Last reviewed: Jul 4, 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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