The Elastic Load Balancer, or ELB, is AWS’s managed load balancing offering. You simply create your load balancer from a variety of load balancer types, classic load balancer, application load balancer, network load balancer, or gateway load balancer. I will go into more detail on the differences between these types in a later post. In short the ELB functions as you’d expect if you are familiar with load balancing your users simply connect to the ELB and the ELB distributes the load across your existing instances. It is much easier, although more expensive, to setup than a traditional load balancer and it integrates with several different AWS features. In terms of security groups your users would connect to your load balancer at 443 or 80 so your load balancer would allow traffic 443 and 80 traffic from anywhere and the that would be forwarded to your EC2 instances, so the instances would allow only 443 and 80 traffic from the security group of your load balancer so there is a level of security as well with utilizing an ELB. Well what if your instances fails, how do you stop the ELB from connecting to it? Well AWS has got you covered there as well. The ELB will perform “health checks” on the instance by periodically connecting over an open port or path, typically port 4567, and ensure it is able to connect successfully, if it fails to connect then the ELB will not forward traffic.