3.1.5.10. Wildcard entry (*)

In DNS, you can set a default entry for undeclared subdomains. Such an entry is called a wildcard.

The entry is created by specifying the symbol * in the subdomain field. The principle of operation of such a record is quite simple — if the requested subdomain, its parent or child subdomain was not explicitly specified in any record, then the wildcard record of the nearest parent will be taken (roughly speaking, the default record). This is useful for setting up a large number of subdomains because you don’t have to add a separate entry for each subdomain. Default when adding or registration domain, two wildcard entries are created: of type A and type AAAA.

For example, for the domain example.com the following records are created:

Subdomain Type Data
example.com A 1.XXX.XXX.XXX
www.example.com A 1.XXX.XXX.XXX
*.example.com A 2.XXX.XXX.XXX
sub.example.com A 3.XXX.XXX.XXX
*.domain.example.com A 4.XXX.XXX.XXX
form.domain.example.com A 5.XXX.XXX.XXX
anothersub.example.com TXT XXXXXXXXXXXX
one.more.example.com TXT XXXXXXXXXXXX

In the case described above, the wildcard entry will be valid for all subdomains, except for:

  • sub — the subdomain was declared because it has records.
  • anothersub — the subdomain was declared because it has records.
  • sub.anothersub — the subdomain was declared because its parent has records.
  • more — the subdomain was declared because its child has records.
  • domain — the subdomain has been declared and has its own wildcard record, which it and all its descendants will use.
  • form.domain — the parent of the subdomain has been declared, therefore the wildcard record of the main name is not used, but the parent has its own wildcard record, which will be used.

Example of return values for different subdomains:

  • Request for www.example.com will return a record 1.XXX.XXX.XXX.
  • Request for sub.example.com will return a record 3.XXX.XXX.XXX.
  • Request for some.sub.example.com will not return the entry because it is not specified. Wildcard entry will not be applied because the subdomain sub was announced.
  • Request for sub.anothersub.example.com will not return the entry because it is not specified. Wildcard entry will not be applied because the subdomain anothersub was announced.
  • Request for anothersub.example.com will return a TXT record XXXXXXXXXXXX.
  • Request for like.domain.example.com will return a record 4.XXX.XXX.XXX.
  • Request for domain.example.com will return a record 4.XXX.XXX.XXX (wildcard entry is used *.domain).
  • Request for form.domain.example.com will return a record 5.XXX.XXX.XXX. Wildcard entry will not be applied because the subdomain form.domain. was announced.
  • Request for test.example.com will return a record 2.XXX.XXX.XXX (wildcard entry is used *).
  • Request for sub.www.example.com will not return the entry because it is not specified. Wildcard entry will not be applied because the subdomain www was announced.
  • Request for poddomen.example.com will return a record 2.XXX.XXX.XXX (wildcard entry is used *).
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