EKS Quickstart does not add cluster tag to a subnet which is already being used by a different EKS cluster

[babarbaig92]

In this specific scenario, I deployed an EKS cluster into an existing VPC. This VPC was already used by another EKS which was also created by Quickstart. Earlier EKS added the tags to the subnets that I provided during the creation of cluster. When I deployed second EKS providing the same subnets, following tag was not created.

kubernetes.io/cluster/your-cluster-name=shared

Due to this problem, ALB ingress controller was not able to create ALB giving the following error.

couldn't auto-discover subnets: unable to discover at least one subnet

I fixed this issue by manually adding the tag kubernetes.io/cluster/your-cluster-name=shared into the subnets and then ALB ingress controller was able to create an ALB.