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Re: Address 127.0.1.1

Thr n convention  as it pertains to the 127.0.0.1 iIP address is that it is meant to be used for testing purposes on a whole. 

Moore information may be found in the links below.

https://www.rfc-editor.org/info/rfc1085


https://www.rfc-editor.org/info/rfc1918



On 5/24/24 10:07, Paul M Foster wrote:

On Fri, May 24, 2024 at 05:22:13PM +0100, Joe wrote:


On Fri, 24 May 2024 11:40:30 -0400
Greg Wooledge <greg@wooledge.org> wrote:


On Fri, May 24, 2024 at 05:22:14PM +0200, Marco Moock wrote:

Am 24.05.2024 um 17:17:45 Uhr schrieb tomas@tuxteam.de:

On Fri, May 24, 2024 at 04:49:18PM +0200, Marco Moock wrote:

[...]

If you operate mail servers, you must have a FQDN. .lan can't be
used for the global DNS stuff, so set a proper FQDN that
belongs to you.

I think this is wrong in that sweeping generality.

In the case it should communicate with other MTAs in the internet,
this will be true because many of them require a resolvable (also
reverse) FQDN in HELO/EHLO that matches the IPv4/IPv6 addresses of
the server.

Most MTAs do not look in /etc/hosts when reading their configuration.
Whatever name they identify with (in the HELO or EHLO command) comes
from some MTA-specific configuration file.

Thus, the contents of /etc/hosts are for *other* things, not related
to MTA configuration.  Just being able to resolve your own hostname
to any address that "works" is the goal.  127.0.1.1 works well for
this, which is why Debian uses it as the default.  If you've got a
static LAN address, you can use that instead.


Long ago, lo used to be just 127.0.0.1, which is what most people would
try to ping to check localhost, and what appeared in /etc/hosts. There
is some subtle reason, which I used to know but have now long forgotten,
why Debian started using 127.0.1.1 in /etc/hosts instead. As far as I'm
aware, any 127. address will resolve to localhost.


My understanding is that 127.0.1.1 is used for hostnames defined by the
user on setup. In setup, you don't specify an IP for your box, so the
hostname goes in the 127.0.1.1. Later, the user can edit the hosts file to
specify a fixed IP if he has one.

Paul
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