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?
The organization should ensure that the IP which is required to receive the ELB traffic is attached to a primary network interface.
It is not possible to attach an instance with two ENIs with ELB as it will give an IP conflict error.
The organization should ensure that the IP which is required to receive the ELB traffic is attached to an additional ENI.
It is not possible to send data to a particular IP as ELB will send to any one EIP.
Explanations:
ELB routes traffic to the primary network interface of instances. For ELB to direct traffic to a specific Elastic IP, that IP must be assigned to the primary network interface.
ELB can register instances with multiple ENIs. However, it routes traffic to the primary network interface, avoiding IP conflicts.
ELB does not support routing traffic specifically to additional ENIs. Traffic is routed to the primary network interface only.
ELB routes traffic consistently to the primary network interface, not randomly to any EIP.
I draft that the answer is:
The organization should ensure that the IP which is required to receive the ELB traffic is attached to a primary network interface.