This document will guide you through the process of setting up your online.net network addresses, DNS servers and rDNS records. For IPv4 we will use systemd-networkd (part of systemd) and odhcp6c (OpenWrt embedded DHCPv6-client) together with iproute2 for IPv6. For DNS we'll use systemd-resolved.
systemd is the default init process on Arch Linux, Debian GNU/Linux, Fedora, Ubuntu and more. iproute2 is also preinstalled there. So, if you're using a distribution that uses systemd, this tutorial should work for you. If you're using Gentoo Linux first make sure that you're using systemd.