Using Cname to point to Elb

[jithin]

Hi Team

In one of the questions I found the explanation that we cannot use Cname record to point to an Elb. Can you explain why choosing a Cname record is incorrect?

Question:

You are the CTO of your co-founded startup where you are building an innovative AI-powered traffic monitoring portal using AWS as its cloud infrastructure. As the system would be used in the entire city, it should be highly available and fault-tolerant to avoid unnecessary downtime.

Which of the following options is the MOST suitable architecture that you should implement?

Use Route 53 and create a CNAME to point to the ELB is incorrect because you have to use an Alias record to route to the ELB and not a CNAME record.

• This discussion was modified 3 years, 6 months ago by  jithin.

[Gerome-TutorialsDojo]

Hello jithin,

Thanks for the feedback.

To put it simply, “Use Route 53 and create an A record to point to the ELB” – means you will create an A-record on Route53, check the box that says “Alias – Yes”, set the value or this A-record to the DNS (CNAME) name of your Load Balancer.

You may recall that you can only point an A-record to an IP address (not CNAME), however, using Route 53 with Alias allows you to create an A-record pointed to a DNS (CNAME) name.

Alias records are similar to CNAME records. Amazon Route 53 alias records provide a Route 53–specific extension to DNS functionality. Alias records let you route traffic to selected AWS resources, such as CloudFront distributions and Amazon S3 buckets. They also let you route traffic from one record in a hosted zone to another record.

Unlike a CNAME record, you can create an alias record at the top node of a DNS namespace, also known as the zone apex. For example, if you register the DNS name example.com, the zone apex is example.com. You can’t create a CNAME record for example.com, but you can create an alias record for example.com that routes traffic to http://www.example.com.

AWS has documentation for this. https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/resource-record-sets-choosing-alias-non-alias.html

AWS recommends that your using Alias pointing to the AWS resources, such as Load Balancers, S3 buckets (web hosting), CloudFront Distributions, etc. In the exam whenever you have the choice to use between an Alias record or CNAME record, you should almost always pick the one using Alias.

Hope this helps.

Let us know if you need further assistance. The Tutorials Dojo team is dedicated to helping you pass your AWS exam!

Regards,

Gerome @ Tutorials Dojo