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
