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Yep. ALIAS records exist basically to get around the CNAME restriction introduced in RFC 1034. Basically, with a CNAME, you can't have any other qtypes for the

Yep. ALIAS records exist basically to get around the CNAME restriction introduced in RFC 1034. Basically, with a CNAME, you can't have any other qtypes for the leaf that you're on. (I'll explain what that means...) For example: If you set up subdomain.yourdomain.com to be an A record to to 10.0.1.1, you can also set up additional A records, AAAA records for IPv6, and even MX and NS records for subdomain.yourdomain.com. If you set up subdomain.yourdomain.com to be a CNAME, you can't have any other record types for subdomain.yourdomain.com. ALIAS records exist because you can't CNAME your root record - the root of your domain has to have at the very least an SOA record, and NS records are going to be needed for the domain to actually resolve. Since those record types exist at the root of your domain, and since CNAME's can't coexist with other record types, you can't use CNAME's at the root of your domain. Accordingly, the ALIAS record really is only useful to redirect the root apex of your domain somewhere else. (Just my two cents.)

brymaster 13y ago
So is this blog incorrect in stating that you can simply change CNAME at your domain's registrar and still take advantage of github's CDN for "apex" domains? http://davidensinger.com/2013/03/setting-the-dns-for-github-pages-on-namecheap/ http://davidensinger.com/2013/03/setting-the-dns-for-github-... Github stated that if you use an "apex" domain your only option is to set A records to their IP but that doesn't seem right.
- namecast 13y ago
  Yeah, that blog isn't right, or at least it shouldn't be. (Just because a DNS registrar allows you to set up @ to point to a CNAME, or www to point to multiple CNAMEs on their authoritative servers, doesn't mean that your recursive nameserver will know what to do with that.) It might be that Namecheap allows you to configure "CNAME's" but actually implements them as ALIAS records or HTTP redirects or something similar and obscures that from the user. Not having a Namecheap account I can't say for certain. GitHub is correct, the @ record cannot be a CNAME.
  - brymaster 13y ago
    Interesting and thanks for the clarification. I see they have (Alias) in parenthesis so it makes me wonder if they are implemented as ALIAS records. This will take some more digging.

brymaster 13y ago

So is this blog incorrect in stating that you can simply change CNAME at your domain's registrar and still take advantage of github's CDN for "apex" domains? http://davidensinger.com/2013/03/setting-the-dns-for-github-pages-on-namecheap/ http://davidensinger.com/2013/03/setting-the-dns-for-github-... Github stated that if you use an "apex" domain your only option is to set A records to their IP but that doesn't seem right.

namecast 13y ago
Yeah, that blog isn't right, or at least it shouldn't be. (Just because a DNS registrar allows you to set up @ to point to a CNAME, or www to point to multiple CNAMEs on their authoritative servers, doesn't mean that your recursive nameserver will know what to do with that.) It might be that Namecheap allows you to configure "CNAME's" but actually implements them as ALIAS records or HTTP redirects or something similar and obscures that from the user. Not having a Namecheap account I can't say for certain. GitHub is correct, the @ record cannot be a CNAME.
- brymaster 13y ago
  Interesting and thanks for the clarification. I see they have (Alias) in parenthesis so it makes me wonder if they are implemented as ALIAS records. This will take some more digging.