How to Connect On-Premises Data Center to Multi-Region GCP VPC?

PCNE By islever Editorial Last updated

Short answer

B Create a Cloud Router and VLAN attachments in the us-east4 region attached to your physical Interconnect in Ashburn, VA. Enable global routing in your VPC.

Question

You are deploying your infrastructure in the us-central1 region. Your on-premises data center is located in New York City, and the Google Cloud region closest to New York City is us-east4. Your Cloud Interconnect is located in Ashburn, Virginia (VA), United States. You need to use Cloud Interconnect to connect your application infrastructure with backend systems in your data center location. You do not expect the application bandwidth to exceed 500 Mbps. You want to minimize latency and cost. What should you do?
  1. Create a Cloud Router and VLAN attachments in the us-east4 region attached to your physical Interconnect in Ashburn, VEnable global routing in your VPC. Set the bandwidth on the VLAN attachments to 500 Mbps.
  2. Create a Cloud Router and VLAN attachments in the us-east4 region attached to your physical Interconnect in Ashburn, VA. Enable global routing in your VPC. Correct Answer
  3. Create a Cloud Router in the us-central1 region and VLAN attachments in the us-east4 region attached to your physical Interconnect in Ashburn, VA. Enable global routing in your VPC.
  4. Create a Cloud Router and VLAN attachments in the us-central1 region attached to your physical Interconnect in Ashburn, VA.

Key Takeaways

Tests regional placement rules for Cloud Interconnect and VPC global routing, with the common trap being the inclusion of explicit bandwidth settings or mismatched router/attachment regions.

This scenario evaluates optimal placement of Cloud Interconnect components and global routing configuration for hybrid cloud deployments. The community consensus confirms that locating VLAN attachments and routers in the nearest region while enabling global routing minimizes latency without unnecessary configuration overhead.

Common mistake: Option A is frequently selected due to the explicit 500 Mbps bandwidth mention, but configuring attachment bandwidth is an optional tuning step that does not establish routing, affect latency, or reduce costs in this architecture.

Expert Analysis

Why the Answer Is Correct

Option B correctly places both the Cloud Router and VLAN attachments in us-east4, the region geographically closest to the New York City on-premises data center, thereby minimizing transit latency. Enabling global routing on the VPC ensures that routes learned from the interconnect are automatically propagated to all regions within the network, including us-central1 where the application infrastructure resides. This configuration aligns with Google Cloud best practices for hybrid connectivity by leveraging automatic route distribution without manual peerings.

Why the Other Options Are Wrong

Option A adds an explicit bandwidth configuration to the VLAN attachment, which is unnecessary for establishing routing paths and does not impact latency or operational costs. Option C violates a core architectural constraint by placing the Cloud Router in us-central1 while keeping the VLAN attachments in us-east4, as they must always reside in the same region. Option D terminates the interconnect in us-central1, forcing traffic to traverse the entire continent and significantly increasing latency compared to the us-east4 termination point.

Community Comment Notes

Comment [1] clarifies that specifying bandwidth adds no real value unless required by a specific provisioning model and can be adjusted later without redesign. Comment [2] reinforces that Option B is superior because it omits the redundant bandwidth parameter while maintaining full routing functionality. Comment [5] suggests Option A might be chosen to reduce costs, but experts note that Dedicated Interconnect pricing tiers typically start at higher thresholds, making the explicit 500 Mbps setting irrelevant for this deployment.

Official Reference

These links open the official vendor documentation in a new tab.

Exam Strategy

Always place Cloud Interconnect VLAN attachments and their corresponding Cloud Routers in the same region, selecting the geographic location closest to your on-premises data center to optimize latency. When evaluating exam options, disregard explicit bandwidth values unless the question specifically addresses provisioning models, as these rarely alter the fundamental network design or cost structure.

Community Votes

B
60%
A
40%

60% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

  1. jfwahab 👍 1 Answered B
    A) Setting bandwidth is not the required configuration step to enable routing between regions. Also, specifying 500 Mbps adds no real value unless you're configuring a Partner Interconnect with a specific provisioning model — and even then, this can be adjusted later. C) Incorrect because the Cloud Router must be in the same region as the VLAN attachments — you cannot create a Cloud Router in us-central1 and attach it to a VLAN in us-east4. D) Also incorrect because Ashburn is in us-east4, and placing the Cloud Router and VLAN in us-central1 won’t work — you must create them in the same region as the Interconnect.
  2. RKS_2021 👍 1 Answered B
    Option B is correct option A: explanation why B is better answer then A. It is mostly correct but unnecessarily mentions setting the VLAN bandwidth explicitly in the answer. This does not change the network design or impact latency/cost significantly.
  3. 09bd94b 👍 1 Answered A
    A is the only option mentioning the bandwith ;-)
  4. b0b25 👍 1 Answered A
    A, reduce the cost - keeping the PI at 500mbps
  5. RKS_2021 👍 1 Answered B
    The charges are same up to 10G.

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