Loopback address
A loopback address is a reserved address a device uses to address itself: 127.0.0.0/8 for IPv4 (commonly 127.0.0.1), defined in RFC 1122, and ::1/128 for IPv6, defined in RFC 4291. Traffic sent to it is handled entirely inside the host's own network stack and never reaches a physical network interface, which is why it keeps working even with no network connection at all. Many services are deliberately configured to listen only on the loopback interface by default, accepting connections from processes on the same machine but refusing anything arriving from outside -- Redis's own "protected mode," for example, falls back to loopback-only access whenever no password is configured. Confirming whether a service is bound to loopback or to a public interface is the first question in diagnosing an unexpected database exposure.
By AdminKit team, Netbase JSC · Updated