Re: 127.0.0.1 deprecated??

[Dennis Ferguson <dennis.c.ferguson%gmail.com@localhost>]

On 20 Oct, 2014, at 13:15 , Mouse <mouse%Rodents-Montreal.ORG@localhost> wrote:
> BUGS
>     Previous versions of the system enabled the loopback interface automati-
>     cally, using a nonstandard Internet address (127.1).  Use of that address
>     is now discouraged; a reserved host address for the local network should
>     be used instead.
> 
> This is the first I've heard of 127.1, a very old syntax for 127.0.0.1,
> being nonstandard for loopback use or of its being deprecated, and,
> indeed, the startup scripts for each of those three versions are
> hardwired to bring lo0 up as 127.0.0.1.

In the first assigned numbers RFC that had the address space divided into
classes, here

    http://tools.ietf.org/html/rfc790#page-4

network 127 was reserved for an unspecified purpose along with the last
class B and class C networks.  127.0.0.1 was just arbitrarily chosen for
the 4.2 BSD lo(4) interface, there was no standard for that.  The 4.2
man page says as much:

    http://modman.unixdev.net/?sektion=4&page=lo&manpath=4.2BSD

The first assigned numbers RFC where network 127 was assigned to
loopback was from the end of 1986:

    http://tools.ietf.org/html/rfc990

Some of the other things they just chose to do in 4.2 BSD, for example
using the all-zeros host address on a subnet as the broadcast address,
ended up being changed later, and I remember the 127.0.0.1 loopback was
not a big hit early on because it was commonly seen on the wire a lot
then and it was hard to figure out who was doing it.  I would guess the
comment on the current man page came from the time when the sentiment
was in favor of having all configured local addresses be real, unique
addresses, and before they officially standardized network 127 with
the (always repeated) restriction that it never appear on the wire.

Dennis Ferguson