- Loopback interface is a logical interface, with no hardware representation.
- It can only be accessed from the local machine, and can only be used to connect to the local machine.
- Every loopback interface gets the IPv4 address 127.0.0.1/8, the localhost address.
- When a program wants to connect to something running on the local machine, it connects to the localhost address.
- Configuring a piece of software to connect to 127.0.0.1 is a sure way to make absolutely certain it connects to the local machine.