This IpAddress is 'the address as known in the outside world' per its description, i.e. the public address a static one-to-one NAT mapping exposes for an internal host. An admin sets this when publishing an internal server to the Internet, since external clients will only ever see and connect to this address, never the real internal one. For example, an admin exposing an internal mail server might set this to 198.51.100.25 so remote senders connect to that address while the server itself keeps its private address.