How to Connect Multiple VPCs to On-Premises via Dedicated Interconnect
A company is planning to connect multiple VPCs in different regions to their on-premises network using a single Dedicated Interconnect. Which TWO configurations are required to achieve this?
Quick Answer
The answer is that you must provision a separate VLAN attachment for each VPC and create a dedicated Cloud Router per VPC. This is required because Dedicated Interconnect provides a single physical connection to your on-premises network, but each VPC needs its own logical termination point—the VLAN attachment—to isolate traffic and routing domains. The Cloud Router, which is a per-VPC resource, then establishes independent BGP sessions over that attachment, allowing each VPC to exchange routes with your on-premises routers without interfering with one another. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how to scale hybrid connectivity across multiple VPCs and regions while avoiding the common trap of assuming a single Cloud Router can serve all VPCs. Remember the key rule: one VLAN attachment and one Cloud Router per VPC, even when sharing the same physical interconnect. A helpful memory tip is “One VPC, one router, one VLAN—share the wire, not the brain.”
⚠ Common exam trap
Google Cloud often tests the misconception that a single Cloud Router or global VLAN attachment can serve multiple VPCs across regions, but in reality, each VPC requires its own regional Cloud Router and VLAN attachment for Dedicated Interconnect.
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 Cloud Router in each VPC
Each VPC requires its own Cloud Router to establish dynamic routing (BGP) over the Dedicated Interconnect. A Cloud Router is a per-VPC resource that manages BGP sessions and routes for that specific VPC, and since the interconnect is shared, each VPC must have its own router to participate in routing independently.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a single Cloud Router for all VPCs
Why it's wrong here
A Cloud Router is attached to a single VPC.
- ✗
Set up Cloud VPN tunnels for regional connectivity
Why it's wrong here
VPN is not needed; Interconnect can connect multiple VPCs with multiple VLAN attachments.
- ✓
Create a Cloud Router in each VPC
Why this is correct
Each VPC needs its own Cloud Router to establish BGP sessions.
- ✗
Use a global VLAN attachment
Why it's wrong here
VLAN attachments are regional, not global.
- ✓
Provision a separate VLAN attachment for each VPC
Why this is correct
Each VPC requires its own VLAN attachment.
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1 more way this is tested on PCNE
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company with multiple VPCs in a Shared VPC environment wants to connect their on-premises network to all VPCs with high availability and minimal cost. They already have a Dedicated Interconnect. What is the most efficient solution?
hard- A.Set up Cloud VPN with dynamic routing to each VPC.
- B.Create an HA VPN gateway for each VPC and peer with on-prem.
- ✓ C.Use the existing Dedicated Interconnect to create multiple VLAN attachments, one per VPC.
- D.Provision a new Partner Interconnect for each VPC.
Why C: A Dedicated Interconnect can support multiple VLAN attachments (each with a separate VLAN ID and BGP session) to connect to different VPCs in a Shared VPC environment. This approach leverages the existing physical connection, provides high availability through redundant attachments, and minimizes cost by avoiding additional circuits or VPN tunnels.
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.