ELB front ending instances running in private subnet of a VPC should reside in a subnet that hast internet gateway association

When creating a ELB for front ending instances running in a private subnet of a VPC, you have to be sure to add the ELB in the subnet(s) that has igw-* (internet gateway) association. If ELB is added to the subnet with NAT association then inbound calls to the private instances from the internet will fail.

Subnet with igw-* association will have igw as part of route table

ELB's availability zone will look like