Knowledge Base

How does DNS work?


DNS can map a server-hostname an addressable machine (by IP address) on the Internet.
A server-hostname may be comprised of a domain name + optional subdomain. (e.g. or
In order to do this, the DNS-Resolver of a computer/client may issue  multiple queries, recursively, until the machine address is resolved.

Example (simplified)

  • A User would like to use his web-browser (Firefox) to visit
  • For this the name needs to be resolved to an IP-Address.
  • A Query/request gets sent to the "resolver"/dns-server configured in the Network Settings.
  • The dns-server asks the root (.) nameservers where com. is and gets an answer (responsible TLD-Servers).
  • The dns-server asks the TLD-Servers where is and gets an answer. (responsible nameservers from a web-host)
  • The dns-server asks the webhost's nameservers what is. The answer is an IP-Address of a web-server.
  • Now the Web-Browser can make a request to the correct webserver and display to his user.

Cached Queries

As a lot of requests/queries are required to resolve a single name to an IP-address.

One of the possible optimizations is for the local resolvers/dns-servers to “cache” results it retrieved before and store them for a specified amount of time.
(This is called TTL…Time To Live)

Important: Due to this mechanism DNS-Updates will take some time to “propagate”. Changes may take up to 24 hours to take full effect.

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