To improve the network performance, you launch a C5 EC2 Amazon Linux instance and enable Enhanced Networking by modifying the instance attribute with “aws ec2 modify-instance-attribute --instance-id instance_id --ena-support”. Which mechanism does the EC2 instance use to enhance the networking capabilities?

Answer options:

A.Intel 82599 Virtual Function (VF) interface.
B.Transit Virtual Interface
C.Elastic Network Adapter (ENA).
D.Elastic Network Interface (ENI).

Correct Answer – C
Enhanced networking has two mechanisms: Elastic Network Adapter (ENA) and Intel 82599 Virtual Function (VF) interface. For ENA, users can enable it with --ena-support.
An EFA is an Elastic Network Adapter (ENA) with added capabilities. It provides all of the functionality of an ENA, with additional OS-bypass functionality. OS-bypass is an access model that allows HPC and machine learning applications to communicate directly with the network interface hardware to provide low-latency, reliable transport functionality."
Option A is incorrect: Because the option of “--ena-support” is not used by Intel 82599 Virtual Function (VF) interface.
Option B is incorrect: Because a Transit Virtual Interface is used to connect resources hosted in an Amazon VPC (using their private IP addresses) through a transit gateway, not suitable for the above scenario.
https://aws.amazon.com/premiumsupport/knowledge-center/public-private-interface-dx/
Option C is CORRECT: In Amazon Linux, users can enable the enhanced networking attribute with the AWS CLI command mentioned in the question.
Option D is incorrect: In this scenario, the mechanism used for enhanced networking should be Elastic Network Adapter (ENA) instead of Elastic Network Interface (ENI).
References:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/enhanced-networking-ena.html.