Troubleshooting the DNS Cache

DNS Resolver

To fully clear the DNS Resolver cache, restart the unbound daemon:

  • Navigate to Status > Services

  • Find unbound in the list

  • Click fa-arrow-rotate-right (restart) or click fa-stop-circle (stop) then fa-play-circle (start)

Restarting the daemon will clear the internal cache, but client PCs may still have cached responses.

Alternately, issue a reload command using the CLI which will flush the cache without stopping the daemon:

unbound-control -c /var/unbound/unbound.conf reload

To selectively clear the DNS Resolver cache at the command line, run:

unbound-control -c /var/unbound/unbound.conf flush <name>

Where <name> is a domain name or hostname to be cleared.

Inspect the contents of the cache from the command line using:

unbound-control -c /var/unbound/unbound.conf dump_cache

DNS Forwarder

To clear the DNS Forwarder cache, restart the dnsmasq daemon:

  • Navigate to Status > Services

  • Find dnsmasq in the list

  • Click fa-arrow-rotate-right (restart) or click fa-stop-circle (stop) then fa-play-circle (start)

Restarting the daemon will clear the internal cache, but client PCs may still have cached responses.

Client DNS Cache

The DNS cache on a Windows PC may be cleaned from a command prompt or Start > Run:

ipconfig /flushdns

This may need to be executed from an Administrator command prompt on Windows Vista and later.

Other operating systems will surely have other means to clear the DNS resolver cache. For example, Ubuntu-based distributions also use dnsmasq, and it may be restarted using:

sudo service network-manager restart

Browsers also have their own internal DNS caches separate from the OS. Close and re-open the browser if none of the above help.

As a last resort, rebooting/restarting a client will surely clear any locally cached data.