SOA-C02 Networking and Content Delivery Practice Question

A company has two VPCs: VPC-A (10.0.0.0/16) and VPC-B (10.1.0.0/16). The VPCs are in the same AWS region. The SysOps administrator needs to enable private IP connectivity between the two VPCs so that an EC2 instance in VPC-A can communicate with an EC2 instance in VPC-B using their private IP addresses. The administrator wants a simple, low-cost solution with high throughput. Which AWS service should be used?

⚠ Common exam trap

Many exam-takers choose AWS Transit Gateway for any multi-VPC connectivity, overlooking that VPC Peering is simpler and cheaper for a two-VPC scenario, and that Transit Gateway’s benefits (centralized routing, transitive peering) are only cost-effective with many VPCs.

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

✓

VPC Peering

VPC Peering is the correct choice because it enables direct, private IP connectivity between two VPCs in the same AWS region using the existing AWS network infrastructure, with no bandwidth bottlenecks, no single point of failure, and no additional cost beyond data transfer. It meets the requirements for simplicity, low cost, and high throughput, as traffic stays within the AWS backbone and does not require a separate transit hub or VPN.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
VPC Peering
Why this is correct
VPC peering establishes a one-to-one network relationship between two VPCs using private IPv4 addresses over AWS's backbone. It requires no virtual appliance, gateway, or physical contract, making it the simplest and most cost-efficient method for a two-VPC scenario in the same region. Since the CIDRs are non-overlapping, route tables can be updated to exchange traffic directly with minimal latency and high throughput.
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AWS Transit Gateway
Why it's wrong here
AWS Transit Gateway is incorrect because, whilst it facilitates private IP connectivity and offers high throughput, it is engineered for complex, large-scale network topologies involving numerous VPCs, hybrid cloud environments, or centralised routing. For a simple connection between only two VPCs, it introduces unnecessary cost and management overhead, failing the "simple, low-cost" requirement of the scenario. It is tempting as it provides the desired connectivity, but it is specifically designed for scaling network connectivity beyond a simple two-VPC peering.
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AWS Direct Connect
Why it's wrong here
AWS Direct Connect is a dedicated physical fiber connection from an on-premises location to an AWS endpoint, not a mechanism for connecting two VPCs. Using it to link VPC A and VPC B would require deploying a Direct Connect gateway, virtual interfaces, and a transit VPC or router, adding infrastructure complexity and monthly costs. The scenario has no on-premises component, so Direct Connect is entirely mismatched for this simple VPC-to-VPC requirement.
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Internet Gateway
Why it's wrong here
Each VPC gets its own Internet Gateway, which is a horizontally scaled, redundant component for enabling inbound and outbound public internet traffic. It does not route traffic between VPCs; any VPC-to-VPC communication would traverse the public internet, losing the private, low-cost, and high-throughput benefits required. An IGW is designed for internet-facing workloads, not for private interconnectivity between VPCs.

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SOA-C02 Networking and Content Delivery Practice Question

Why each option matters

Option-by-option breakdown

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