5 ms·

I've seen .local and .lan DNS suffixes and assumed that they were specified in a standard somewhere. Perhaps not.

cpburns2009 8y ago
I don't think they're standard. The RFC references "Special-Use Domain Names" [1] which contains a list of special use domains. I'm confused about ".local" though. It's reserved for Multicast DNS? [2] [1]: https://www.iana.org/assignments/special-use-domain-names/special-use-domain-names.xhtml https://www.iana.org/assignments/special-use-domain-names/sp... [2]: https://tools.ietf.org/html/rfc6762#page-67 https://tools.ietf.org/html/rfc6762#page-67
- sigjuice 8y ago
  Multicast DNS is the special use.
- djsumdog 8y ago
  .local has always been confusing
  - sigjuice 8y ago
    Resolving a .local domain name works like this. $ dig -p 5353 raspberrypi.local @224.0.0.251 ; <<>> DiG 9.8.3-P1 <<>> -p 5353 raspberrypi.local @224.0.0.251 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21640 ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;raspberrypi.local. IN A ;; ANSWER SECTION: raspberrypi.local. 10 IN A 192.168.1.175 A DNS query packet is to the multicast address 224.0.0.251 and UDP port 5353. All devices on your network that are listening on that address will see the query (e.g. Linux systems with avahi-daemon or Macs running mDNSResponder). The device whose name is raspberryi will respond. RFC6762 should have all the details.
    - 8_hours_ago 8y ago
      This is the best explanation of how mDNS works that I've ever seen. Thank you!
    - cookiecaper 8y ago
      mDNS is cool and all, but I wish they would've picked a slightly-more-specific TLD. ".local" is the natural suffix for LANs, and making computers confused about whether they should resolve that via multicast or standard DNS techniques wasn't very nice. Something like ".mdns" or ".zeroconf" would've been a lot better.
      - WorldMaker 8y ago
        mDNS is roughly the equivalent of going door-to-door in the LAN and asking anybody if they've heard of "Greg", so it I don't think it is that confusing that it gets .local, especially given the circumstances that lead to relying on mDNS in that most LANs don't have authoritative DNS servers.
        cookiecaper 8y ago
        It's not that the name doesn't make sense, it's just that it collides with a very common TLD for LANs. It shouldn't be squatting on a name humans want to use. Computers are unlikely to do the correct thing when you ping a .local on a network that uses that suffix, because they have to decide how to handle the potential name collision (which is still somewhat frequent, more than 15 years later).
        WorldMaker 8y ago
        It's the other way around, though? .local's usage on LANs prior to the RFC was squatting on a non-reserved TLD. The RFC finally reserved the TLD for an appropriate usage. The name applies equally to both usages, the usages can live side-by-side, and the RFC is even kind enough to support that (though as you point out frequently don't always work as expected), even though it didn't need to take into account backwards compatibility with "squatters".
amckinlay 8y ago
.local is used ad-hoc by mDNS (Apple). Last time the issue of naming local-area devices came up on ##networking, the consensus was to purchase a domain name in order to name local network devices without interfering with global name resolution standards, which seems ridiculous.
- icebraining 8y ago
  I think you can use .localhost freely.
  - amckinlay 8y ago
    .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...).
sigjuice 8y ago
.lan is non-standard, likely fabricated by your router. .local is RFC6762.
LeoPanthera 8y ago
.local is used by zeroconf/rendezvous/bonjour/whatever it is called today, and so its explicit use as a LAN TLD is discouraged. If you try to set it in pfSense, for example, it warns you not to.
ktpsns 8y ago
Another wide-spread non-standarized TLD is .box. It is used by Fritz!Box home routers (https://en.wikipedia.org/wiki/Fritz!Box https://en.wikipedia.org/wiki/Fritz!Box). They are shipped with a really good operating system and handle the resolution of .box very seamless, integrating all the names of registering DHCP devices (i.e. you can resolve your-iphone.box in your LAN). The TLD stems from the "pun" http://fritz.box http://fritz.box.

cpburns2009 8y ago

I don't think they're standard. The RFC references "Special-Use Domain Names" [1] which contains a list of special use domains. I'm confused about ".local" though. It's reserved for Multicast DNS? [2] [1]: https://www.iana.org/assignments/special-use-domain-names/special-use-domain-names.xhtml https://www.iana.org/assignments/special-use-domain-names/sp... [2]: https://tools.ietf.org/html/rfc6762#page-67 https://tools.ietf.org/html/rfc6762#page-67

sigjuice 8y ago
Multicast DNS is the special use.
djsumdog 8y ago
.local has always been confusing
- sigjuice 8y ago
  Resolving a .local domain name works like this. $ dig -p 5353 raspberrypi.local @224.0.0.251 ; <<>> DiG 9.8.3-P1 <<>> -p 5353 raspberrypi.local @224.0.0.251 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21640 ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;raspberrypi.local. IN A ;; ANSWER SECTION: raspberrypi.local. 10 IN A 192.168.1.175 A DNS query packet is to the multicast address 224.0.0.251 and UDP port 5353. All devices on your network that are listening on that address will see the query (e.g. Linux systems with avahi-daemon or Macs running mDNSResponder). The device whose name is raspberryi will respond. RFC6762 should have all the details.
  - 8_hours_ago 8y ago
    This is the best explanation of how mDNS works that I've ever seen. Thank you!
  - cookiecaper 8y ago
    mDNS is cool and all, but I wish they would've picked a slightly-more-specific TLD. ".local" is the natural suffix for LANs, and making computers confused about whether they should resolve that via multicast or standard DNS techniques wasn't very nice. Something like ".mdns" or ".zeroconf" would've been a lot better.
    - WorldMaker 8y ago
      mDNS is roughly the equivalent of going door-to-door in the LAN and asking anybody if they've heard of "Greg", so it I don't think it is that confusing that it gets .local, especially given the circumstances that lead to relying on mDNS in that most LANs don't have authoritative DNS servers.
      - cookiecaper 8y ago
        It's not that the name doesn't make sense, it's just that it collides with a very common TLD for LANs. It shouldn't be squatting on a name humans want to use. Computers are unlikely to do the correct thing when you ping a .local on a network that uses that suffix, because they have to decide how to handle the potential name collision (which is still somewhat frequent, more than 15 years later).
        WorldMaker 8y ago
        It's the other way around, though? .local's usage on LANs prior to the RFC was squatting on a non-reserved TLD. The RFC finally reserved the TLD for an appropriate usage. The name applies equally to both usages, the usages can live side-by-side, and the RFC is even kind enough to support that (though as you point out frequently don't always work as expected), even though it didn't need to take into account backwards compatibility with "squatters".

amckinlay 8y ago

.local is used ad-hoc by mDNS (Apple). Last time the issue of naming local-area devices came up on ##networking, the consensus was to purchase a domain name in order to name local network devices without interfering with global name resolution standards, which seems ridiculous.

icebraining 8y ago
I think you can use .localhost freely.
- amckinlay 8y ago
  .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...).

sigjuice 8y ago

.lan is non-standard, likely fabricated by your router. .local is RFC6762.

LeoPanthera 8y ago

.local is used by zeroconf/rendezvous/bonjour/whatever it is called today, and so its explicit use as a LAN TLD is discouraged. If you try to set it in pfSense, for example, it warns you not to.

ktpsns 8y ago

Another wide-spread non-standarized TLD is .box. It is used by Fritz!Box home routers (https://en.wikipedia.org/wiki/Fritz!Box https://en.wikipedia.org/wiki/Fritz!Box). They are shipped with a really good operating system and handle the resolution of .box very seamless, integrating all the names of registering DHCP devices (i.e. you can resolve your-iphone.box in your LAN). The TLD stems from the "pun" http://fritz.box http://fritz.box.