Setup: ddclient

ddclient is a widely used DynDNS client that comes with many Linux distributions and is also pre-installed on some routers.

After ddclient has been installed, the file /etc/ddclient.conf has to be configured as follows:
protocol=dyndns2
server=dyndns.inwx.com
login=your-dyndns-login
password=your-dyndns-passwort
your.dyndns-hostname.com