Re: [gentoo-user] Why do we add the local host name to the 127.0.0.1 / ::1 entry in the /etc/hosts file?

[Grant Taylor <gtaylor@gentoo.tnetconsulting.net>]

On 3/10/21 9:38 AM, Michael wrote:
> I always thought the localhost class A addresses were from days of old 
> 'inter- network' era.  The difference with 127.0.0.1 and a private 
> LAN address is the 127.0.0.1 does not reach the data link layer, 
> but loops-back at IP layer 3 and responds to any applications on the 
> local PC.  So, I understood this to mean it never went through the 
> whole network stack, as it does when you ping a remote host.

The 127/8 (formerly called a class A) network is reserved / allocated 
for a host to communicate with itself.

However, /how/ local addresses are used is entirely implementation 
specific.  This goes for both 127.0.0.1 and other addresses bound to 
local network cards.

Linux will not send traffic to the local LAN IP to the NIC either.  But 
that's a /Linux/ /implementation/ detail.  Other OSs, e.g. Windows, 
don't use a loopback adapter for 127.0.0.1.  Instead it's purely a 
software construct.  But that's a /Windows/ /implementation/ detail.

Aside:  Windows (2k and onward) does have a loopback adapter that you 
can optionally install.  However you /can't/ assign 127.0.0.1 (or any 
127/8) to it.  It is meant to be used like Linux uses the dummy adapter.



-- 
Grant. . . .
unix || die