A network interface is a virtual network attachment that gives an instance network connectivity and associated private or public IP addresses. An EC2 instance can use multiple interfaces for separate networks, additional addresses, or specialized appliances. section 3.7
Configure an additional interface in the EC2 console:
- Open EC2, choose Network Interfaces, note the instance’s subnet ID, and select Create Network Interface. section 3.7
- Provide a description, select the existing subnet and security group, and enable automatic private IPv4 assignment. section 3.7
- After the interface becomes Available, attach it to the instance, then associate an additional public IP address if required. section 3.7
Separating two web-server networks
An EC2 web server can attach two interfaces in different subnets, such as an application network and a management network. Linux exposes them as interfaces such as eth0 and eth1; HTTP virtual hosts can bind each address to a different document root. section 3.7
Multiple interfaces also support legacy clients that require separate TLS/SSL certificates when SNI cannot be used. Lambda functions can receive interfaces in selected VPC subnets and security groups to reach private resources, but this adds complexity and should be necessary-driven. section 3.7 section 6.2.4
