An organization is planning to create a secure scalable application with AWS VPC and ELB. The
organization has two instances already running and each instance has an ENI attached to it in
addition to a primary network interface. The primary network interface and additional ENI both
have an elastic IP attached to it.
If those instances are registered with ELB and the organization wants ELB to send data to a
particular EIP of the instance, how can they achieve this?

A.
The organization should ensure that the IP which is required to receive the ELB traffic is attached
to a primary network interface.

B.
It is not possible to attach an instance with two ENIs with ELB as it will give an IP conflict error.

C.
The organization should ensure that the IP which is required to receive the ELB traffic is attached
to an additional ENI.

D.
It is not possible to send data to a particular IP as ELB will send to any one EIP.

Explanation:
Amazon Virtual Private Cloud (Amazon VPC) allows the user to define a virtual networking
environment in a private, isolated section of the Amazon Web Services (AWS) cloud. The user
has complete control over the virtual networking environment. Within this virtual private cloud, the
user can launch AWS resources, such as an ELB, and EC2 instances. There are two ELBs
available with VPC: internet facing and internal (private) ELB. For the internet facing ELB it is
required that the ELB should be in a public subnet. When the user registers a multi-homed
instance (an instance that has an Elastic Network Interface (ENI) attached) with a load balancer,
the load balancer will route the traffic to the IP address of the primary network interface (eth0).

http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/gs-ec2VPC.html