This is exactly the logic that I was operating under: A.B.EXAMPLE.COM <http://a.b.example.com/>. is a subdomain, but it should never be referred to as a subdomain of EXAMPLE.COM <http://example.com/>. It is only a subdomain of B.EXAMPLE.COM <http://b.example.com/>.
On Fri, Feb 28, 2025 at 12:11 PM Jay <mysi...@gmail.com> wrote: > On Fri, Feb 28, 2025 at 10:05 AM Stephane Bortzmeyer via NANOG > <nanog@nanog.org> wrote: > > On Tue, Feb 25, 2025 at 07:36:16AM -0500, > > Yes. I believe the confusion is that some documentation, > APIs, or software incorrectly obfuscate the concept of a domain > and take that the domain is only the part registered with a domain > registrar. > > E.g. "EXAMPLE.COM" would be a domain, and in "B.C.EXAMPLE.COM" > the C.EXAMPLE.COM would be disregarded and considered part of Example.com > leading to the strange claims that you have a "B.C" subdomain of > example.com > or that B.c.example.com is a subdomain of example.com > But that would be completely non-standard. > > Every subdomain is in fact a domain name. And every domain under the root > is a subdomain of the label directly above it and ONLY the one > specific DNS label > directly above that particular subdomain. > > And the management or registration structure of the DNS; the zone > boundaries users > refer to, have nothing to do with which names are actually a domain or > subdomain. > > A subdomain is exclusively the direct descendent of another domain > which is observed solely by the addition of one dot and label on the > lefthand side. > > Take for example: A.B.EXAMPLE.COM. Assume that FQDN exists. > > Given that exists you are guaranteed that A.B.EXAMPLE.COM. is a domain, > B.EXAMPLE.COM. is a domain, EXAMPLE.COM. is a domain, COM. > is a domain, and . is a domain. > > A.B.EXAMPLE.COM. is a subdomain, but it should never be referred to > as a subdomain of EXAMPLE.COM. It is only a subdomain of B.EXAMPLE.COM. > > > -- > -J >
