ANS-C01 Question 428
Single answerYou are designing a hybrid network that connects your on-premises data center to your AWS environment using an AWS Direct Connect (DX) connection. Your on-premises network uses an MTU (Maximum Transmission Unit) of 1500 bytes, while the AWS side of the connection supports an MTU of up to 9001 bytes (jumbo frames). How should you configure frame sizes to optimize bandwidth utilization and reduce fragmentation across this connection?
- A
Configure the MTU on both sides to 1500 bytes to ensure compatibility.
- B
Configure the MTU on the AWS side to 9001 bytes and leave the on-premises MTU at 1500 bytes.
- C
Enable Path MTU Discovery (PMTUD) and configure the AWS side to use an MTU of 9001 bytes.
- D
Set the MTU on the AWS side to 1500 bytes to match the on-premises MTU and avoid fragmentation.
Show answer and explanation
Correct answer: C
Explanation
Path MTU Discovery (PMTUD) is the recommended approach because it dynamically adjusts the MTU size based on the smallest MTU in the path, ensuring that packets are not fragmented. By enabling PMTUD and configuring the AWS side to use a larger MTU (e.g., 9001 bytes), you can optimize bandwidth utilization on the AWS side while avoiding fragmentation caused by smaller MTUs on the on-premises side.
- A. Incorrect.
This ensures compatibility between the two networks, but it does not optimize bandwidth utilization since larger frame sizes on the AWS side could reduce overhead.
- B. Incorrect.
This configuration would cause fragmentation since the on-premises MTU is smaller than the AWS MTU, leading to inefficiencies.
- C. Correct.
Using Path MTU Discovery (PMTUD) allows dynamic detection of the optimal MTU size across the connection, minimizing fragmentation while utilizing larger frame sizes where possible.
- D. Incorrect.
While this avoids fragmentation, it does not take advantage of the AWS jumbo frame capability, missing the opportunity to optimize bandwidth utilization.