AWS/Route53/S3: Redirecting www.example.com to example.com works. Redirecting example.com to www.example.com doesn’t

The key trick in setting up a subdomain is linking the subdomain with the parent domain through a set of name servers - NS records. I.e. the subdomain.example.com is known to its set of nameservers (NS records) and the parent domain example.com must know what these NS are for the subdomain. Just like in GoDaddy where you set the example.com's Route53 NS that are then inserted into the .com zone as a link to your domain. Makes sense?

This is how you create a subdomain in Route53:

1. Create new Hosted Zone subdomain.example.com in Route53 and copy the set of **NS records* to a clipboard or Notepad or somewhere:

   

   (I'm using my domain aws.nz for this demo - example.com subdomain can't be created in R53)

2. The open example.com hosted zone details (or aws.nz in this case) and click Create Record Set. Set:

   • Name: subdomain.example.com
   • Type: NS
   • Value: the list of nameservers from step 1 above.

   

3. Create some record in subdomain, e.g. test.subdomain.example.com=192.0.2.123, wait a minute and try to resolve it:

   ~ $ host test.subdomain.aws.nz
   test.subdomain.aws.nz has address 192.0.2.123
   

Hope that helps :)

CNAME is never allowed at the apex of a zone, so that is the immediate cause of this failure, but that is somewhat unimportant, because for what you are doing, a CNAME isn't the correct record type.

If you have the record www.example.com A 203.0.113.1 and you want example.com to always return the same answer as www.example.com (currently 203.0.113.1 but you of course automatically updated if www changes in the future) then the example.com record would need to be type A with Alias = Yes and the alias target set to www.example.com.

This is exactly the same as just setting both hostnames to be normal A records and giving them the same value for IP address, except that changing one doesn't automatically change the other if you do them both manually, so having one of them as an alias for the other is usually preferrable.

The confuaion probably comes from a long-standing practice of doing something like this:

example com     A     203.0.113.1
www.example.com CNAME example.com.

This in less efficient since some lookups require twice the round trip time, so the alias approach is still preferred.

An Alias is a better solution, since it's an internal pointer to another record inside Route 53 whereas a CNAME is (in the sense relevant here) an external pointer to another record which could be anywhere. Aliases always point to the same type of record, A to A, AAAA to AAAA, CNAME to CNAME, so even if you had been allowed to create that invalid CNAME at the apex, the next problem would have been that the target of the alias wasn't a CNAME.