SCS-C02 Question 225
Single answerYour company has deployed a VPC in AWS and established a Site-to-Site VPN connection between the VPC and your on-premises data center. The VPN connection appears to be up, but traffic from on-premises servers is not reaching the EC2 instances in the VPC. What could be causing this issue?
- A
The Security Group attached to the EC2 instances is not allowing inbound traffic from the on-premises network.
- B
The Site-to-Site VPN connection is not configured with a pre-shared key.
- C
The on-premises firewall is blocking traffic to the VPC CIDR range.
- D
The VPC route table is missing a route to the on-premises network through the Virtual Private Gateway.
Show answer and explanation
Correct answer: D
Explanation
In a Site-to-Site VPN connection, the VPC route table must include a route to the on-premises network through the Virtual Private Gateway. Without this route, the traffic will not be directed correctly, even if the VPN connection is 'up.' Ensuring proper routing configurations in the VPC route table is critical for establishing successful communication between on-premises systems and VPC resources.
- A. Incorrect.
The Security Group attached to the EC2 instances could restrict traffic, but this would only block traffic at the instance level. The issue described is related to traffic not reaching the VPC at all, not an instance-specific issue.
- B. Incorrect.
Site-to-Site VPN connections use a pre-shared key for authentication, but if the VPN connection is 'up,' this means the pre-shared key is already correctly configured. This is not the root cause of the issue.
- C. Incorrect.
The on-premises firewall could block traffic to the VPC CIDR range, but this would need to be verified. However, this is not the most likely cause described in the scenario involving route tables.
- D. Correct.
If the VPC route table does not include a route to the on-premises network through the Virtual Private Gateway, traffic from the VPC to the on-premises network (or vice versa) will not be routed correctly. This is the most likely cause based on the scenario.