How to: How do you restrict an AWS ELB to certain source ips:
Add the following metadata annotation to your LoadBalancer service with a comma separated list of CIDRs:
```
service.beta.kubernetes.io/load-balancer-source-ranges
```
Each ELB gets its own security group and this annotation will add those CIDR addresses to the allowed source IPs

https://github.com/kubernetes/kubernetes/blob/d95b9238877d5a74895189069121328c16e420f5/pkg/api/service/annotations.go#L27-L34