1.1.1.1: Fast, privacy-first consumer DNS service

TIL you can also use 1.1 and it will expand to 1.0.0.1

  $> ping 1.1

  PING 1.1 (1.0.0.1) 56(84) bytes of data.
  64 bytes from 1.0.0.1: icmp_seq=1 ttl=55 time=28.3 ms
  64 bytes from 1.0.0.1: icmp_seq=2 ttl=55 time=33.0 ms
  64 bytes from 1.0.0.1: icmp_seq=3 ttl=55 time=43.6 ms
  64 bytes from 1.0.0.1: icmp_seq=4 ttl=55 time=41.7 ms
  64 bytes from 1.0.0.1: icmp_seq=5 ttl=55 time=56.5 ms
  64 bytes from 1.0.0.1: icmp_seq=6 ttl=55 time=38.4 ms
  64 bytes from 1.0.0.1: icmp_seq=7 ttl=55 time=34.8 ms
  64 bytes from 1.0.0.1: icmp_seq=8 ttl=55 time=45.7 ms
  64 bytes from 1.0.0.1: icmp_seq=9 ttl=55 time=45.2 ms
  64 bytes from 1.0.0.1: icmp_seq=10 ttl=55 time=43.1 ms

You can also use the decimal value of the IP, without the dots: https://16843009

  1.2 -> 1.0.0.2
  1.2.3 -> 1.2.0.3

But then, much of software would fail here - Firefox/Chrome for example would both threat that as bareword and redirect to search page.

You can also sing that number to the tune of the famous 8675309 song with very little robato.

The most useful case for this shortcut is 127.1 -> 127.0.0.1

Interesting question related to this : https://superuser.com/questions/486788/why-does-pinging-192-...

It work as expected if you give it the http://1.2.3 schema prefix.

The input bar is a search bar in modern browsers.

Or if you follow it with a trailing slash, for less typing

  1.1/

Don't try that in the wild, most sw out there would ignore spec and use some arbitrary regex to validate IP format.

i.e python:

    octets = ip_str.split('.')
    if len(octets) != 4:
        raise AddressValueError("Expected 4 octets in %r" % ip_str)

Where have you been all my life?

Sitting at 127.1, apparently.

Hex works too: https://0x1010101

What spec says that 127.1 and 127.0.0.1 are equivalent?

I don’t actually think it’s in a spec formally but is in a common c lib[0].

> a.b

> Part a specifies the first byte of the binary address. Part b is interpreted as a 24-bit value that defines the rightmost three bytes of the binary address. This notation is suitable for specifying (outmoded) Class C network addresses.

[0]: https://linux.die.net/man/3/inet_aton

Sadly, binary / octal don't work: https://0b1000000010000000100000001 / https://0o100200401

Octal works, with the older 0-prefix convention: https://0100200401

0, which is a shorthand for 0.0.0.0 is likely the most code-golf-y way to write localhost, as many [EDIT: Linux] systems alias 0.0.0.0 to 127.0.0.1:

  $ ping 0
  PING 0 (127.0.0.1) 56(84) bytes of data.
  64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.032 ms

Of course, don't expect this to work universally. A lot of software will try to be clever with input validation, and fail.

Tangentially related: https://fosdem.org/2018/schedule/event/email_address_quiz/

Thanks. I just came across the man page myself while I was writing this tiny program.

  $ cat 127.1.c
  #include <stdio.h>
  #include <arpa/inet.h>
   
  int main(int argc, char *argv[])
  {
      struct in_addr addr;
   
      if (inet_aton(argv[1], &addr))
          printf("%08x\n", addr.s_addr);
   
      return 0;
  }
  $ make 127.1 CFLAGS=-Wall
  cc -Wall     127.1.c   -o 127.1
  $ ./127.1 1.1
  01000001
  $ ./127.1 127.1
  0100007f

Stays unaliased on macOS:

My-MacBook-Pro:bottle mrkstu$ ping 0 PING 0 (0.0.0.0): 56 data bytes ping: sendto: No route to host

You are right, I faithfully assumed it's a spec without checking. Thanks.

It's not fully true that 127.0.0.1 is the same as 0.0.0.0. For example, binding a webserver to 0.0.0.0 make it on the public network while 127.0.0.1 is strictly localhost.

0.0.0.0 is not localhost. It's "any address".

The POSIX spec (IEEE 1003.1) says the same thing for inet_addr(), so it does occur in an actual spec.

Yes, you're right.

What I was trying to say is - On Linux, INADDR_ANY (0.0.0.0) supplied to connect() or sendto() calls is treated as a synonym for INADDR_LOOPBACK (127.0.0.1) address.

Not so for bind() or course.

If you want to memorize the integer, it's not a bad mechanic to use... Why do you hate me?

However ping to 127.1 works the same as localhost.

I just upvoted you, bc (a) funny and (b) TIL a new word (rubato).

Or if you prefix it with //

  //1.1.1.1

It's one more letter than a suffix, but as a prefix its a bit clearer. I've known companies to post LAN hostname addresses that way, and in written/printed materials it stands out pretty clearly as an address to type.

It follows the URL standards (no schema implies current or default schema). Many auto-linking tools (such as a Markdown, Word) recognize it by default (though sometimes results are unpredictable given schema assumptions). It's also increasingly the recommendation for HTML resources where you do want to help insure same-schema requests (good example cross-server/CDN CSS and JS links now are typically written as //css-host.example.com/some/css/file.css).

Ah, I had completely forgotten about that. Thanks!