The loopback IP range starts at 127.0.0.0 and reaches to 127.255.255.255. The IP stack automatically short-circuits any packets that are sent to a loopback IP, and never puts them onto a real network. Instead, the packets get routed to the localhost
, the network interface
that the packets were sent from.
The loopback IP exists independently of any of the interfaces contactable IP addresses
, and is always available, even if the interface is down (this is due to the fact that the packets sent to a loopback IP are intercepted in the software TCP/IP stack
, and never makes it to the hardware interface).