The following concepts are essential in understanding ENIs and how to use. You should read them before using ENIs.
Primary ENIs and Secondary ENIs
- The ENI that is automatically created when you create a CVM instance is the primary ENI.
- ENIs created by users are secondary ENIs.
- The primary ENI cannot be unbound, while secondary ENIs can.
Primary Private IP Addresses
- The primary private IP address of an ENI can be randomly assigned by the system or defined by users when the ENI is created.
- The primary private IP address of the primary ENI can be modified, while that of a secondary ENI cannot be modified.
Secondary Private IP Addresses
- A secondary private IP address is any private IP address other than the primary private IP address. You can configure secondary private IP addresses when you create or edit an ENI.
- A secondary private IP address can be bound and unbound.
EIPs are bound to the ENI private IP addresses one to one.
Multiple security groups can bind to an ENI.
An ENI has a globally unique MAC address.