Custom Domain DNS Addresses And Name Addressing Conventions

Periodically, when reviewing the many problem reports about Google Custom Domains, and especially those reporting the ubiquitous "Another blog ..." error message, we'll look at the DNS configuration and see a partial DNS setup
www.mydomain.com. 900 IN CNAME ghs.google.com.

yet the blogger reporting the problem states
I setup my domain with both the root, and the "www" alias, defined. This is what I setup! Whatever can the problem be?

mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 900 IN CNAME ghs.google.com.

We look deeper, and find not the above, but
mydomain.com.mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 900 IN CNAME ghs.google.com.

or maybe
mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com.mydomain.com. 900 IN CNAME ghs.google.com.

SAY WHAT?

This is a typical problem with many GUI Domain Managers, where "mydomain.com" is already known to the wizard (look at the top of the Domain Manager display). When you specify a "CNAME" for "www.mydomain.com", in the "CNAMES (Aliases)" entry, you don't specify "www.mydomain.com", you simply specify "www". Specifying "www.mydomain.com" for "CNAMES (Aliases)" results in
www.mydomain.com.mydomain.com. 900 IN CNAME ghs.google.com.

Similarly, specifying "mydomain.com" for "A (Host)" results in
mydomain.com.mydomain.com. 900 IN CNAME ghs.google.com.

This will not always be the case, unfortunately. Some DNS Manager wizards automatically extract redundant "mydomain.com" phrases from the "A (Host)" and "CNAMES (Aliases)" entries. Others, like GoDaddy, do not.

For GoDaddy and some (not all) similar wizards
  • To designate "mydomain.com": Enter "@" (that's a Shift-2, on most keyboards), under "A (Host)".
  • To designate "www.mydomain.com": Enter "www", under "CNAMES (Aliases)".

If you have a third party DNS Host (not eNom or GoDaddy), you are responsible for finding out how they signify the domain root, when entering the "A (Host)" and "CNAMES (Aliases)" records. Try and prevent
mydomain.com.mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 900 IN CNAME ghs.google.com.

or
mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com.mydomain.com. 900 IN CNAME ghs.google.com.

and eliminate one possible cause for the "Another blog ..." error.

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