Assigning Static IP Address to AWS Load Balancer

Question

How can I assign a static IP address to a ELB. Seems like I cannot.

Some articles online asks to create a Route 53 record but this requires changing CNAME of domain which also redirect email traffic. I just want to change A record not CNAME.

Some articles also mention that I can use a EC2 instance as a reverse proxy. But will a single proxy be able to handle a lot of traffic?

Any solution for this?

Answer 1

AWS' Elastic Load Balancer is actually elastic on two levels as described here: http://shlomoswidler.com/2009/07/elastic-in-elastic-load-balancing-elb.html

The first level is the load balancer itself. In order to make sure that ELB can scale to whatever volume you have and burst to whatever volume you suddenly encounter, AWS assigns a 'static' DNS hostname (e.g. MyDomainELB-918273645.us-east-1.elb.amazonaws.com). That hostname points to multiple IP addresses. You can see that (from a command line) by running

$ host MyDomainELB-918273645.us-east-1.elb.amazonaws.com MyDomainELB-918273645.us-east-1.elb.amazonaws.com 172.31.7.2 MyDomainELB-918273645.us-east-1.elb.amazonaws.com 172.31.11.33 

The second form of elasticity within the ELB is obviously then ELB directing the query to one of your EC2 instances in the pool.

So, you can see that trying to assign a static IP address to the load balancer would be self-defeating.

Using an EC2 instance as a reverse proxy would also seem self-defeating as you would then create a bottleneck before even getting to the ELB. Might as well just create your own load balancer.

The recommended solution (which you've pointed out) is to create a CNAME that points to the ELB hostname (which won't change).

i.e. my-app.mycompany.com -> MyDomainELB-918273645.us-east-1.elb.amazonaws.com

This would allow you to integrate your scalable application, behind the ELB within your domain.

I'm not sure I fully understand why you cannot create a CNAME in your DNS or what that has to do with directing email traffic, can you explain?

Answer 2

A new feature in AWS (I believe it was announced at Re:Invent 2017) allows for static IPs with Network Load Balancers (NLB). NLB can only handle layer 4 (TCP) and not HTTP specifics (layer 7).

You can assign one Elastic IP address per availability zone.

For details see the AWS blog post or the NLB documentation.

The "Classic Load Balancer" and "Application Load Balancer" do not support static IPs. If you need a feature only provided by those, you have to fall back to the CNAME solution described above.