This document describes key concepts of Elastic Network Interface (ENI).
Primary or Secondary ENIs
An ENI that is automatically created when a Cloud Virtual Machine (CVM) is created in a Virtual Private Cloud (VPC) is the primary ENI.
An ENI that is manually created by the user is a secondary ENI.
The binding and unbinding operations are supported for secondary ENIs instead of primary ENIs.
Primary Private IP Address
When an ENI is created, take note of the following items about the primary private IP address of the ENI:
The primary private IP address of the primary ENI is randomly assigned by the system and can be modified after creation.
The primary private IP address of a secondary ENI can be randomly assigned by the system or specified by the user, but cannot be modified after creation.
Secondary Private IP Address
In addition to the primary private IP address, the secondary private IP addresses bound to an ENI are configured by the user when the user creates or modifies the ENI.
The binding and unbinding operations are supported for secondary private IP addresses.
EIP
Each EIP is bound to a private IP address of an ENI.
Security Group
One or more security groups can be bound to an ENI. You can configure appropriate security groups for an ENI based on actual business requirements.
MAC Address
Each ENI has a globally unique Media Access Control (MAC) address.