How to use external DNS in conjunction with an AWS Elastic Load Balancer

amazon ec2amazon-elbamazon-route53amazon-web-servicesdomain-name-system

I'm setting up an Application Elastic Load Balancer, and I have it pointing to a few EC2 instances. I'm now trying to get my head around how to set up the DNS, given that my DNS is hosted externally from AWS.

I understand that I can use the cname for my domain, so I can set up DNS records for www.example.com, foo.example.com (and any other sub-domain.example.com) and point those to my ELB which something like elb-123456789.eu-west-1.elb.amazonaws.com. So this is all fine.

However, for the apex record (example.com) I cannot use cname, and I must use an A record. As far as I can see (and I could be wrong on this), I need to use Route 53:

Create a hosted zone for example.com
Create a recordset inside that hosted zone for example.com, with a type of alias. For the alias target, I select the ELB from above
Click Save
???

I have no idea how to now point my A record at my domain registrar to this Route 53 alias.

Or am I meant to be doing something completely different?

Best Answer

DNS standards say you can't have a CNAME at the domain Apex, you need an A record.

Some providers will let you do this against standards. CloudFlare does this in a tricky way, it appears to let you create a CNAME at the domain apex but does it in a way that's standards compliant using a proxy system - Michael explains it well below.

The best option is to use AWS Route53 and alias records. Route53 takes over the job of providing DNS for the domain, you no longer need your previous DNS provider.

Related Solutions

Nginx AWS ELB – How to Set Real IP from AWS ELB Load Balancer Address

If you can guarantee that all requests will be coming from ELB (I'm not familiar with it), you could try:

real_ip_header X-Forwarded-For;
set_real_ip_from 0.0.0.0/0;

That should tell nginx to trust an X-Forwarded-For header from anyone. The downside is that if anyone directly accesses your server, they would be able to spoof an X-Forwarded-For header and nginx would use the wrong client ip address.

Amazon Route 53 – How to Create a Zone Apex Alias for Elastic Load Balancer

A engineer on the Route 53 team informed me that creating the proprietary alias can be created in the Route 53 Console (the GUI).

Here are the steps.

click create record set
for zone apex record just leave the name field blank
select the type of alias you want to make A or AAAA (all steps after this are the same for both types)
Select the yes radio button.
Open the EC2 console in another tab and navigate to the list of your load balancers.
Click on the load balancer and look at the description tab in the pane below the list. Sample output below

DNS Name: new-balancer-751654286.us-east-1.elb.amazonaws.com (A Record)
ipv6.new-balancer-751654286.us-east-1.elb.amazonaws.com (AAAA Record)
dualstack.new-balancer-751654286.us-east-1.elb.amazonaws.com (A or AAAA Record)

Note: Because the set of IP addresses associated with a LoadBalancer can change over time, you should never create an “A” record with any specific IP address. If you want to use a friendly DNS name for your LoadBalancer instead of the name generated by the Elastic Load Balancing service, you should create a CNAME record for the LoadBalancer DNS name, or use Amazon Route 53 to create a hosted zone. For more information, see the Using Domain Names With Elastic Load Balancing at http://docs.amazonwebservices.com/ElasticLoadBalancing/latest/DeveloperGuide/using-domain-names-with-elb.html.

Status: 0 of 0 instances in service

Port Configuration: 80 (HTTP) forwarding to 80 (HTTP)

Stickiness: Disabled(edit)

Availability Zones: us-east-1b

Source Security Group: amazon-elb-sg

Owner Alias: amazon-elb

Hosted Zone ID: Z3DZXD0Q79N41H

Now copy the Hosted zone ID in the above case ‘ Z3DZXD0Q79N41H’ and paste it into the field labeled ‘Alias Hosted Zone ID:’
Now copy the DNS Name in the above case ‘ new-balancer-751654286.us-east-1.elb.amazonaws.com‘ and paste into the field ‘ Alias DNS Name:’ -Just an FYI this DNS name is the same for both A and AAAA alias records. (do not use ‘ ipv6.new-balancer-751654286.us-east-1.elb.amazonaws.com‘)
Click create record set or at this time you can select yes to weight the record and provide a weight between 0-255 and a setID such as ‘my load balancer’

Best Answer

Related Solutions

Nginx AWS ELB – How to Set Real IP from AWS ELB Load Balancer Address

Amazon Route 53 – How to Create a Zone Apex Alias for Elastic Load Balancer

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