DNS: CNAME at the apex – “CNAME and other data”

What the message looks like

dns_master_load: example.com.zone:12: example.com: CNAME and other data

Common causes

• A hoster or SaaS provider asks for “CNAME to app.provider.net”, including the root domain.
• The zone editor rejects the entry or BIND refuses to load the zone.
• A provider accepts it anyway – then MX or TXT lookups break unpredictably.
• CNAME and TXT on the same subdomain name, e.g. for a verification.

Check

1. Check the zone file for errors (BIND)
   named-checkzone example.com /etc/bind/db.example.comCopy
2. Show existing records at the apex
   dig example.com CNAME +short; dig example.com SOA +short; dig example.com MX +shortCopy
3. Get the provider's target IP
   dig app.provider.net A +shortCopy

Fix

• For the root domain set A and AAAA records with the provider's IPs.
• If your DNS provider supports it: use ALIAS, ANAME or CNAME flattening instead of a CNAME.
• Redirect the root domain to www via HTTP and create only www as CNAME.
• On subdomains never mix a CNAME with other records of the same name.
• Check the zone after changes and lower the TTL before switching.

FAQ

Why does a CNAME work on www but not on example.com?

www has no other records, so a CNAME is allowed. The apex always needs SOA and NS, and nothing else may sit next to a CNAME.

What does CNAME flattening do?

The DNS provider resolves the target itself and serves A and AAAA records at the apex. To resolvers it looks like a normal A record.