DNS – Type of the record CNAME

  DNS, DNS theory, Records of DNS

CNAME record indicates that the domain is alias other domains in the sense that they have a common DNS record (not common web content, etc.).

If for the alias domain exists this record, it shall not exist any other. Example:

www1.domain.cz.  1800  IN  CNAME  domain.cz.
www2.domain.cz.  1800  IN  CNAME  domain.cz.
www3.domain.cz.  1800  IN  CNAME  domain.cz.
domain.cz.       1800  IN  A
domain.cz.       1800  IN  MX     10 mail.domain.cz

Here are subdomains www1, www2 and www3 as aliases for domain.cz and all of them have IP address and also the same MX record. The sense of CNAME record is evident – have a real IP address and any other records only in one place and to change them is not necessary to rewrite all domains separately.