3 ms·

.localhost is the loopback IP on most resolvers, though.

• icebraining 8y ago
  "localhost" by itself is, but second-level domains (ex.: laptop.localhost) aren't, at least not anywhere I've tried it.
  • WorldMaker 8y ago
    In a well-configured machine second-level domains for .localhost are also supposed to loopback, per the RFC. (It's useful as a development tool as you can Virtual Host project1.localhost and project2.localhost to different in development sites if your OS and server support it, which tend to be in similar ways to how they generally support Virtual Hosts.)
  • yrro 8y ago
    RFC6761 says: 6.3. Domain Name Reservation Considerations for "localhost." The domain "localhost." and any names falling within ".localhost." are special in the following ways: 1. Users are free to use localhost names as they would any other domain names. Users may assume that IPv4 and IPv6 address queries for localhost names will always resolve to the respective IP loopback address. [...] 3. Name resolution APIs and libraries SHOULD recognize localhost names as special and SHOULD always return the IP loopback address for address queries and negative responses for all other query types. Name resolution APIs SHOULD NOT send queries for localhost names to their configured caching DNS server(s). And goes on to specify how resolvers, authoratitive DNS servers, registrars, etc. should behave. This is implemented on my machine at least by systemd_resolved, see https://github.com/systemd/systemd/blob/master/src/resolve/resolved-dns-synthesize.c#L379 https://github.com/systemd/systemd/blob/master/src/resolve/r... which returns ::1/127.0.0.1 for any record for which which is_localhost is true (defined in https://github.com/systemd/systemd/blob/master/src/basic/hostname-util.c#L164 https://github.com/systemd/systemd/blob/master/src/basic/hos...).