PCNE Implementing Hybrid Interconnectivity Practice Question
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?
⚠ Common exam trap
A common misconception in Google Cloud is 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.
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
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.
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.
- ✗
Configure the VPN gateway to advertise the subnets
Why it's wrong here
The VPN gateway does not handle BGP advertisements; Cloud Router does.
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.
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.