DNS (Domain Name System) is a distributed naming system that provides information about resources using domain names. To open a Joomla website, a browser normally needs the server IP address obtained through DNS.
How DNS works
A recursive DNS resolver finds an answer for the client and caches it. When necessary, it queries other servers, including the authoritative servers for the zone. An authoritative server holds domain records rather than the website files.
A record has a TTL, which specifies how long the answer may be cached. After a change, visitors can therefore receive different answers for a while. Delegation changes and cached negative answers also affect the result.
Common record types
- A maps a name to an IPv4 address, while AAAA maps it to an IPv6 address.
- CNAME identifies another domain name as the canonical name for an alias.
- MX identifies the domain mail servers.
- TXT stores text data, for example domain verification information and email policies.
- NS identifies authoritative name servers.
DNS and Joomla websites
Moving Joomla usually involves updating the relevant address records while preserving email and other service records. A correct A record does not guarantee a working website: the web server, HTTPS and application must also work.
When a Joomla domain is unavailable, check name resolution separately from the server response. DNS failures occur before PHP runs, so changing Joomla settings cannot repair incorrect domain delegation.
Conclusion
DNS connects names to network resources. Checking DNS separately from hosting helps identify the source of availability problems.