ENI-visible mode allows you to bind an Elastic IP Address (EIP) to a secondary elastic network interface (ENI), replacing its private IP address to enable direct internet access. Learn about its limitations and configuration requirements.-Cloud Architect Design Tools(CADT)-阿里云帮助中心

Learn how to enable ENI-visible mode in Cloud Architect Design Tool (CADT).

How it works

ENI-visible mode allows you to bind an Elastic IP Address (EIP) to a secondary elastic network interface (ENI) so the EIP is visible within the operating system. In this mode, the EIP directly replaces the original private IP address of the secondary ENI. The interface then functions exclusively for public network traffic, effectively becoming a "public-only NIC". As a result, you can view the EIP address directly on the ECS instance by running commands such as ifconfig or ip addr show.

Key features

This mode only supports binding to a secondary elastic network interface, not to a primary network interface or an ECS instance.
After you bind the EIP, it replaces the private IP address of the secondary ENI, and the interface can no longer be used for private network communication.
Supports all IP protocols, such as SIP, active mode FTP, DNS, and H.323, because traffic does not undergo NAT translation.
The EIP provides direct internet access without requiring a route table lookup.

Procedure

In your CADT architecture diagram, connect the EIP resource to a secondary ENI attached to an ECS instance.
Double-click the connection line to open the properties panel on the right.
From the Binding Mode drop-down list, select ENI-visible mode.
After you deploy the architecture, CADT binds the EIP to the secondary ENI in visible mode.

Note: Ensure the selected ECS instance type supports multiple network interfaces and a secondary ENI has already been created.

Limitations and considerations

This mode is not recommended for new users. Alibaba Cloud recommends using a secondary CIDR block for a similar outcome.
Starting April 23, 2026, an EIP in ENI-visible mode cannot access the CIDR block reserved for Alibaba Cloud services, 100.64.0.0/10, which is used for internal endpoints for services such as OSS and RDS. To ensure business continuity, you must configure a route beforehand to direct this traffic to the primary network interface.
In this mode, you can bind a secondary elastic network interface to only one EIP.
Some ECS images cannot automatically detect the IP address of a secondary network interface. You may need to manually configure the network and routes.