A Practical Guide to Domain Names and DNS
The system that turns a domain name into the servers behind it, through records such as A, AAAA, CNAME, MX and TXT held at a DNS provider.
Marcus Adeyemi
The key figures
- A and AAAA records
- point a name at an IPv4 or IPv6 address
- CNAME record
- points one name at another; the DNS standard does not allow it at the zone apex
- MX records
- direct the domain's email to mail servers
- TXT records
- hold verification strings and email authentication data such as SPF
- TTL
- how long resolvers may cache a record before asking again
Why this is worth getting right
DNS mistakes take whole sites and mailboxes offline, and during a migration they are the step most often done at the wrong moment or forgotten.
Do this, not that
Do
- Lower TTLs a day or two before planned changes
- Save a copy of every record before editing the zone
- Check email records whenever the web host or nameservers change
- Protect the registrar account with two-factor sign-in and a transfer lock
- Keep auto-renew on and track renewal dates
Don’t
- Moving nameservers without recreating the email records
- Letting a domain lapse because the card on file expired
- Leaving the domain in a former employee's or agency's account
- Changing records at the start of a busy trading day
When to bring in help
Our advice Bring in help before moving nameservers or hosting, when email stops arriving after a change, or when nobody on the team can access the registrar account.
Where this comes from
- Cloudflare Learning Center — What is DNS?
- Cloudflare Learning Center — DNS records
- RFC Editor — RFC 1034 Domain names: concepts and facilities
The figures and practices above come from the sources listed.
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