<p>Is it always possible to ping localhost and it resolves to 127.0.0.1?</p>

<p>I know Windows Vista, XP, Ubuntu and Debian do it but does everyone do it?</p>

Any correct implementation of TCP/IP will reserve the address 127.0.0.1 to refer to the local machine. However, the mapping of the name "localhost" to that address is generally dependent on the system
```
hosts
```
file. If you were to remove the localhost entry from
```
hosts
```
, then the localhost name may no longer resolve properly at all.