Why can’t I use a CNAME record on the root domain?

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Answer: This is a limitation defined by the DNS standard, not a platform restriction.

Explanation:

  • The root domain (e.g. a.example.com) must contain mandatory DNS records such as:

  • SOA (Start of Authority)

  • NS (Name Server)

  • According to DNS specifications:

    A CNAME record cannot coexist with any other record type Since the root domain must have SOA and NS records, it cannot be assigned a CNAME record.

Recommended configuration:

  • Use A or AAAA records for the root domain
  • Use CNAME records for subdomains

Example:

Domain Type Value
a.example.com A 1.2.3.4
www.a.example.com CNAME a.example.com

Additional note:

Some DNS providers offer ALIAS / ANAME records to simulate root-level CNAME functionality. These are proprietary extensions and not part of the DNS standard.

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