Elastic IP (EIP) and Elastic Network Interface (ENI)

Elastic IPs (EIPs)

  • A public IP address that can be “moved”
  • Enables instances without a public IP to become accessible from the Internet

Good to know:

  • EIPs are region specific
  • IPv6 not currently supported
  • Two-step process to implement: allocation and association
  • Upon association, any previous public IP is released (DNS hostname changes as well)
  • Can be disassociated and reassociated with another instance
  • Two-step process to remove: disassociate and release

You are charged when:

  • Elastic IPs not associated;
  • More than one Elastic IP on an instance


Elastic Network Interfaces (ENIs)

Virtual network card that can include:

  • Primary and secondary private IPv4 addresses
  • An Elastic IP address (IPv4)
  • A public IPv4 address
  • Public IPv6 addresses
  • Security groups
  • MAC address Description

Good to know:

  • Every instance in a VPC has a default network interface, called the primary network interface (eth0). You cannot detach a primary network interface from an instance.
  • When detaching and reattaching to instances, the attributes and traffic follow the interface.
  • You can modify attributes after creation (security groups and IP addresses).