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If i have a site with url www.example.com, is possible to have another subdomain with the subdomain www? for example www.extra.example.com. I don't sure about this.

I tried to find some information, but i don't have enough experience in that area

user1783933
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2 Answers2

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qux.bar.foo.example.com

com is the top-level domain,
example is the second-level domain,
foo is the third-level domain,
bar is the fourth-level domain,
qux is the fifth-level domain.

And yes, you can have more levels (DNS calls them "labels").

Many people mean only the third-level domain when they say "subdomain" (or fourth-level domain in case of an effective top-level domain like co.uk), probably because most domains don’t have more levels, however:

foo is the subdomain of example.com,
bar is the subdomain of foo.example.com,
qux is the subdomain of bar.foo.example.com.

By the way, www is no special label, just a convention.

Community
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unor
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Yes it is. In your example, the two sub-domains "www" and "www.extra" are different.

Julian Knight
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  • But, the whole "www.extra" is a subdomain? Or is it a sub sub domain? some hosting services has restrictions for the subdomain www. Is possible anyway have two subdomains? – user1783933 Nov 21 '14 at 13:23
  • Well strictly anything in front of the domain is a sub-domain. The RFC doesn't add any restrictions and there is no requirement to use (or not use) www, that is just common convention. But you are right, some services apply unnecessary restrictions that may prevent certain combinations. But you can absolutely have as many sub-domains as you like, that is the whole point. Those can point to the same or a different physical location as you want. It is a very flexible approach. – Julian Knight Nov 21 '14 at 15:47
  • Your domain is `example.com` and `www` is a sub domain. – Luke Nov 22 '14 at 01:54