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All about ENI for AWS Exam and later
- An ENI (Elastic Network Interface) is a logical networking component in a VPC that represents a virtual network interface card (NIC).
- If ENI, think virtual NIC.
- An ENI can include the following attributes:
- a primary private IPv4 address
- one or more secondary private IPv4 addresses
- one Elastic IP address per private IPv4 address
- one public IPv4 address, which can be auto-assigned to the network interface for eth0 when you launch an instance
- one or more IPv6 addresses
- one or more security groups
- a MAC address
- a source/destination check flag
- a description
- You can create an ENI, attach it to an instance, detach it from an instance, and attach it to another instance in the same subnet.
- Multiple Elastic IP addresses can be applied to an ENI.
- Multiple IP addresses can be assigned to an ENI.
- An ENI has a dynamically assigned private address in the assigned subnet, and can optionally have a dynamically assigned public IP address as well.
- You can create and configure ENIs in your account and attach them to instances in your VPC.
- An ENI's attributes follow it as it is attached or detached from an instance and reattached to another instance.
- When you move an ENI from one instance to another, network traffic is redirected to the new instance.
- You can also modify the attributes of your ENI, including changing its security groups and managing its IP addresses.
- Each instance in your VPC has a default network interface, called the primary network interface (eth0) that is assigned a private IPv4 address from the IPv4 address range of your VPC. You cannot detach this primary network interface from an instance.
- You can create and attach an additional network interface (i.e ENI here) to any instance in your VPC. The number of network interfaces you can attach varies by instance type.
- Attaching multiple network interfaces to an instance is useful when you want to:
- Create a management network.
- Use network and security appliances in your VPC.
- Create dual-homed instances with workloads/roles on distinct subnets.
- Create a low-budget, high-availability solution.