How to set AWS ALB instead of ELB in Istio?

Current accepted answer is correct. However I would like to give a slight update to it. Once AWS alb controller is installed and configured there are several steps one should take to make it work and be usable:

1. Use istioctl manifest generate command to generate a list of manifests
2. Find istio-ingressgateway service configuration
3. Update it to be of a NodePort type
4. Update ports configuration to have a pre-defined mapping of Node and Target ports. Note the status-port NodePort
5. Apply these manifests instead of installing/updating istio using istioctl install command. In some cases it might be better to rely on istio helm installation though
6. Update ingress configuration to have the following annotations

      alb.ingress.kubernetes.io/healthcheck-port: 'PORT'
      alb.ingress.kubernetes.io/healthcheck-path: /healthz/ready
      alb.ingress.kubernetes.io/healthcheck-protocol: HTTP```
where PORT equals to the istio status-port NodePort value 

This way, you update ALB default configuration for the healthcheck to check Istio healthcheck 

Step 1 : Change istioingresssgateway service type as nodeport

Step 2 : Install ALB ingress controller

Step 3 : Write ingress.yaml for istioingressgateway as follows:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  namespace: istio-system
  name: ingress
  labels:
    app: ingress
  annotations:
    kubernetes.io/ingress.class: alb
    alb.ingress.kubernetes.io/scheme: internet-facing
    alb.ingress.kubernetes.io/subnets: <subnet1>,<subnet2>
spec:
  rules:
    - http:
        paths:
          - path: /*
            backend:
              serviceName: istio-ingressgateway
              servicePort: 80

alb.ingress.kubernetes.io/subnets annotation can be avoided if you labelled subnet of vpc with :

kubernetes.io/cluster/: owned

kubernetes.io/role/internal-elb: 1 (for internal ELB)

kubernetes.io/role/elb: 1 (for external ELB)

or else you can provide two subnet values and each subnet should be in different availability zone in the above yaml

It worked in Istio 1.6