Key Concepts

Last updated: 2020-06-24 16:09:31

    Before using an ENI, you need to understand the following concepts:

    Primary ENIs and Secondary ENIs

    • The ENI that is automatically created when a CVM is created in a VPC 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

    When an ENI is created:

    • The primary private IP address of the primary ENI is randomly assigned, which can be modified.
    • The primary private IP address of the secondary ENI is randomly assigned or customized, which 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.

    Security Groups

    An ENI can be bound with one or more security groups.

    MAC Addresses

    An ENI has a globally unique MAC address.