Continuing from the previous pattern of managing the network traffic by way of routing, we will move to managing the traffic through distinct interfaces. As with physical machines it is possible to have multiple network interfaces.

In the previous pattern, the machine relied on a single interface for all traffic in and out. We might extend on this instead of having two interfaces: one to be responsible for all the traffic to and from the outside internet and the other would be responsible for the traffic to an on-site data center. This alternate network traffic is sometimes referred to as a backnet or management network.

By creating our interfaces in this fashion there is a clear distinction of responsibilities and separation of concerns. Also, this makes it much easier to apply AWS-provided firewall configurations or Security Groups. Security Groups are provided as a first-class AWS configuration that acts as firewall rules to other AWS entities such as EC2 instances...