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Elastic Compute Service

Network interface and IP address

Overview of network interface

Description

A network interface is also called a virtual network interface (VNI). In the Virtual Private Cloud (VPC), a network interface is a network interface mounted on cloud resources like Elastic Compute Service (ECS) or Classic Load Balancer. It serves as an essential component for enabling network communication.

Each network interface has one primary private IP address. If necessary, multiple secondary private IP addresses can be manually allocated to it. For details, refer to IP address overview.

Network interface types

Type	Description
Primary network interface	The primary network interface is generated by default when creating an ECS instance. It cannot be detached from the ECS and is automatically deleted along with the ECS instance.
Secondary network interface	The secondary network interface is manually created by the user, supporting mount, unmount, and delete operations, offering flexibility.
VolcanoEngine Network Interface	The VolcanoEngine Network Interface is automatically created by the system when you create services such as Transit Router (TR) or NAT Gateway. It enables private network connectivity for backend services. You can only modify the tags of the VolcanoEngine Network Interface. You cannot delete, mount, or unmount the VolcanoEngine Network Interface. The lifecycle of the VolcanoEngine Network Interface is aligned with that of the associated ECS instance.

Applicable scenarios

Building high-availability clusters

Multiple network interfaces can be deployed on a single ECS instance to build a high-availability architecture, thereby improving system stability and reliability.

Low-cost failover

The private IP address, EIP, and security group rules of a secondary network interface are all closely associated with the secondary network interface. In the event of a failure, the secondary network interface can be unmounted from the failed ECS instance and mounted to a standby ECS instance. This allows for the rapid transfer of business traffic from the failed instance to the standby one, enabling quick service recovery.

Granular traffic management

You can configure multiple network interfaces on an ECS instance and use different interfaces for different scenarios, such as internal access and Internet-facing services. Precise security group rules can be configured for each network interface based on business scenarios to effectively control the traffic direction of each network interface.

Multiple private IP addresses for a single ECS instance

Multiple private IP addresses can be assigned to the network interfaces of an ECS instance. If your ECS instance hosts multiple applications, a separate external IP address can be assigned to each application, which significantly enhances the utilization of the ECS instance.

Multiple EIPs for a single ECS instance

When multiple IP addresses are assigned to a network interface of an ECS instance, multiple EIPs can be associated with those IP addresses. This helps prevent business interruptions caused by blocked EIPs.

Limits

You can mount a secondary network interface to only one ECS instance.

The number of private IPv4 addresses and private IPv6 addresses that you can assign to the primary network interface or to any secondary network interface mounted to an ECS instance is limited by the private IP address quota of a single network interface. The quota is determined based on the ECS instance type.

For example, you can assign up to six private IPv4 addresses (including the primary private IPv4 address) and six private IPv6 addresses to the primary or secondary network interface of an ECS instance whose type is ecs.g3i.large.

You can manually assign up to nine secondary private IPv4 addresses and ten private IPv6 addresses to a secondary network interface that has never been mounted to an ECS instance.

You can associate each private IPv4 address of a network interface with an EIP.

By default, IPv6 addresses of a network interface only support private network communication. To access the Internet over IPv6, you need to first enable IPv6 Internet access.

tip

IPv6 gateways and Dual-Stack VPC are currently in beta. Only accounts that have completed enterprise authentication can apply for a trial. If you need a trial, contact your account manager.

Each network interface has only one globally unique MAC address.

For more information about network interface limits, refer to Limits.

Configuration procedure

Secondary network interface

Primary network interface

If you need to assign and configure secondary private IPv4 or IPv6 addresses for the secondary network interface, perform the following steps:

Create a secondary network interface.

Mount the secondary network interface to an ECS instance.

Configure the secondary network interface for the ECS instance.

(Optional) Assign and configure secondary private IPv4 or IPv6 addresses for the secondary network interface.

IPv4:

Assign IPv4 addresses.

Configure private IPv4 addresses for the ECS instance.

If the IP addresses assigned to the secondary network interface need to communicate with the Internet, you can associate EIPs with the IP addresses.

IPv6:

Assign IPv6 addresses.

Configure private IPv6 addresses for the ECS instance.

If the IP addresses assigned to the secondary network interface need to communicate with the Internet, you can enable IPv6 Internet bandwidth.

Delete the network interface.

Last updated: 2026.06.18 17:49:50