2. Amazon Elastic Compute Clouds (EC2)

IP Addresses

Placement Groups

Elastic Network Interfaces

NAT Gateway vs NAT Instances

Instance Lifecycle

Billing and Provisioning Options

AWS Nitro System and Enclaves

Misc

Explore

Elastic Network Interfaces

An Elastic Network Interface (ENI) is a logical networking component within a Virtual Private Cloud (VPC) in AWS, representing a virtual network card. ENIs can be attached to EC2 instances, providing them with various networking capabilities.

Here's an overview of ENIs and their key features:

Attributes:

Primary Private IPv4 Address: Assigned from the IPv4 address range of your VPC.

Secondary Private IPv4 Addresses: Additional IPv4 addresses within the VPC's address range.

Elastic IP Address (IPv4): One Elastic IP address per private IPv4 address.

Public IPv4 Address: Optionally assigned.

IPv6 Addresses: Optionally assigned.

Security Groups: Controls inbound and outbound traffic.

MAC Address: Unique hardware identifier.

Source/Destination Check Flag: Network traffic validation.

Description: Optional description for identification.

ENI Management:

ENIs can be created and configured in your AWS account.

You can attach ENIs to EC2 instances to provide additional networking capabilities.

The primary network interface (eth0) is automatically created when launching an instance and cannot be moved or detached.

Additional ENIs can be attached to instances, with the number depending on instance family/type.

ENIs are bound to a specific Availability Zone (AZ) and can be specified during creation.

You can specify IP addresses manually or auto-assign them.

Hot, warm, or cold attachment of ENIs is supported, depending on instance state.

Attachment Behavior:

Default interfaces (e.g., eth0) are terminated with instance termination.

Manually added interfaces are not terminated by default, but you can change this behavior.

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Enhanced Networking

Elastic Network Adapter (ENA):

Enhances networking performance by providing higher bandwidth and lower latency.

Enabled via SR-IOV and compatible with specific instance types.

Supports higher packet-per-second (PPS) performance.

Must launch an HVM AMI with appropriate drivers.

Elastic Fabric Adapter (EFA):

Builds upon ENA capabilities with OS bypass functionality.

Supports high-performance computing (HPC) and machine learning (ML) workloads.

Enhances inter-instance communication for scaling applications.

Good for Tightly coupled applications.

Available at no additional cost and compatible with all supported EC2 instances.

Choosing Between ENI, ENA, and EFA

ENI:

Basic adapter type for standard networking requirements.

Compatible with all instance types.

ENA:

Suitable for higher bandwidth and lower latency requirements.

Supported for specific instance types with HVM AMIs.

EFA:

Designed for HPC, MPI, and ML workloads with high inter-node communication demands.

Compatible with all supported EC2 instances, providing OS bypass functionality.

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