Elastic Network Interface (ENI)

Slides
c03 ec2 elastic network interface

If and how many secondary network cards can be added depends on the machine type.

Network Interface associations

These can be attached to a primary network interface:

  • MAC address (always)

  • Primary IPv4 private address

  • 0 or more secondary IPv4 private addresses

  • 0 or 1 public IPv4 address (= 1 per interface) (Not Elastic IP address)

  • 1 Elastic IP Address per private IP address (= 1 per private IPv4 address)

  • 0 or more IPv6 addresses

  • 1 or more security groups

  • Source/Destination ckeck

Secondary ENIs have same resources support as the primary but can be moved from an instance to another.

Since they can be moved from an instance to another, if you have a software that attaches its license to the MAC address you can easily port it.

DNS

Private

If enabled the private IPv4 address is pointed to by a private DNS record that can only be resolved within the VPC.

E.g.: 10.16.0.10 ⇒ 10-16-0-10.ec2.internal

Public

If enabled the public IPv4 address is pointed to bya public DNS record.

E.g.: 3.15.65.124 ⇒ something like ec2-3-15-65-124.compute-1.amazonaws.com

But inside the VPC the DNS name will resolve to the private IPv4 address of the primary network interface while to the public IPv4 outside it.