David Hopwood david.nospam.hopwood@REDACTED
Thu Apr 13 03:56:04 CEST 2006

Marthin Laubscher wrote:
> I don't believe it's a case of shorthand, 127.1 is the same thing as
>, which is why win telnet considers 127.1 as a legal address and
> reports in that manner. 
> Try ping (incl. win) and you'll see more of what goes on
> Ping   -> pinging
> Ping 192.168.72     -> pinging
> Ping 192.11010120   -> pinging
> Ping 323223559      -> pinging
> Believing that the numbers in the dotted notation are "octets" will get you
> thinking that you can specify an ipv4 address in less than for octets, which
> isn't the case. It's always 4 octets. In the decimal, dotted string format
> we use, it can be specified in any one of the four formats equally (pseudo
> notation, don't try to parse this in Erlang".
>   "<<A:8>>.<<B:8>>.<<C:8>>.<<D:8>>"
> =="<<A:8>>.<<B:8>>.<<C:16>>"
> =="<<A:8>>.<<B:24>>.
> =="<<A:32>>"

Note that you won't find this notation in any RFC, AFAIK. It's a Unix
(originally BSD) thing; not an IETF standard.

>From RFC 1020:

   One commonly used notation for internet host addresses divides the
   32-bit address into four 8-bit fields and specifies the value of each
   field as a decimal number with the fields separated by periods.  This
   is called the "dotted decimal" notation.  For example, the internet
   address of VENERA.ISI.EDU in dotted decimal is, or

(whereas inet_aton would interpret the components of as

When IETF protocols make use of string representations of IP addresses,
they generally only specify the full dotted-decimal notation, without
shorthands, octal, or hexadecimal. For example, "" is
a valid URL, but "http://323223559/" isn't. Most browsers get this wrong,
because they (directly or indirectly) use inet_aton, and don't bother to
validate URLs properly. Personally, I think it's unfortunate that the APIs
of Erlang and some other recent languages are perpetuating this misfeature,
and would recommend stripping it out.

David Hopwood <david.nospam.hopwood@REDACTED>

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