LO(4)                                                                    LO(4)



NAME
       lo - software loopback network interface

SYNOPSIS
       pseudo-device loop

DESCRIPTION
       The  _l_o_o_p  interface is a software loopback mechanism which may be used
       for performance analysis, software testing, and/or local communication.
       As with other network interfaces, the loopback interface must have net‐
       work addresses assigned for each address family with which it is to  be
       used.   These  addresses  may  be  set  or changed with the SIOCSIFADDR
       ioctl.  The loopback interface should be the last interface configured,
       as  protocols  may  use  the order of configuration as an indication of
       priority.  The loopback should never  be  configured  first  unless  no
       hardware interfaces exist.

DIAGNOSTICS
       lo%d:  can’’t  handle  af%d.   The  interface  was handed a message with
       addresses formatted in an unsuitable address  family;  the  packet  was
       dropped.

SEE ALSO
       intro(4N), inet(4F), ns(4F)

BUGS
       Previous versions of the system enabled the loopback interface automat‐
       ically, using a nonstandard Internet  address  (127.1).   Use  of  that
       address  is now discouraged; a reserved host address for the local net‐
       work should be used instead.



4.2 Berkeley Distribution        May 21, 1986                            LO(4)