Takes a boolean argument, or the special value "route". When true, the domain name received from the DHCP server will be used as DNS search domain over this link, similar to the effect of the Domains= setting. If set to "route", the domain name received from the DHCP server will be used for routing DNS queries only, but not for searching, similar to the effect of the Domains= setting when the argument is prefixed with "~". Defaults to false.
It is recommended to enable this option only on trusted networks, as setting this affects resolution of all host names, in particular of single-label names. It is generally safer to use the supplied domain only as routing domain, rather than as search domain, in order to not have it affect local resolution of single-label names.
A boolean or "resolve". When true, enables Link-Local Multicast Name Resolution on the link. When set to "resolve", only resolution is enabled, but not host registration and announcement. Defaults to true.
but LLMNR also resolves single-label names. Can anyone explain this?
Source: https://www.freedesktop.org/software/systemd/man/systemd.network.html as of systemd version 239.