In fact they are somewhat "supported" as there are some reserved domains that you can use as they won't have an external meaning. https://tools.ietf.org/id/dra

In fact they are somewhat "supported" as there are some reserved domains that you can use as they won't have an external meaning. https://tools.ietf.org/id/draft-chapin-rfc2606bis-00.html#new https://tools.ietf.org/id/draft-chapin-rfc2606bis-00.html#ne... Consider putting your "local" hostnames under .localdomain .domain .lan .home .host or .corp Personally I think .lan and .corp are the best options.