What is the collaborative working mechanism between ENI and NAT gateway?

The collaborative working mechanism between an Elastic Network Interface (ENI) and a NAT Gateway involves enabling private subnet resources to access the internet securely while maintaining a private IP address for internal communication.

An ENI is a virtual network interface that can be attached to an EC2 instance or other compute resources within a VPC. It provides a primary private IP address and can have secondary IP addresses, security groups, and MAC addresses.

A NAT Gateway is a managed service that allows instances in a private subnet to connect to the internet or other AWS services without exposing their private IPs. It translates private IP addresses to a public IP address for outbound traffic and routes responses back to the private instance.

How They Work Together:

1. Private Subnet Setup: An EC2 instance is launched in a private subnet and attached to an ENI with a private IP.
2. NAT Gateway Deployment: A NAT Gateway is deployed in a public subnet within the same VPC. The NAT Gateway itself has an Elastic IP (EIP) for internet access.
3. Route Table Configuration: The private subnet's route table is updated to direct internet-bound traffic (0.0.0.0/0) to the NAT Gateway.
4. Traffic Flow: When the EC2 instance sends a request to the internet, the traffic exits through the ENI, routes via the NAT Gateway, and gets translated to the NAT Gateway's public IP. Responses return through the NAT Gateway and reach the instance via the ENI.

Example:

A web server in a private subnet needs to download updates from the internet. The server’s ENI is attached to the instance, and the private subnet routes traffic to a NAT Gateway. The NAT Gateway forwards the request using its EIP, retrieves the updates, and sends them back to the server via the ENI.

For similar functionality in Tencent Cloud, you can use Elastic Network Interface (ENI) and NAT Gateway services to achieve secure internet access for private instances.