Newer releases of systemd contain a change that removes not the part after the first dot but the part after the last when determining the interface name (apparently some interface names actually contain a dot). This changes the default prefix to only contain one dot and avoids the dots added by IPv4 addresses to create a unique interface/protocol for each DNS server (it also replaces the `:` in IPv6 addresses with something that might cause less conflicts). References strongswan/strongswan#1353