LO(4)		    UNIX Programmer's Manual		    LO(4)



NAME
     lo - software loopback network interface

SYNOPSIS
     /sys/conf/SYSTEM:
	  NLOOP     _1	 # loop-back pseudo-device

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 inter-
     faces, the loopback interface must have network addresses
     assigned for each address family with which it is to be
     used.  These addresses may be set or changed with the SIOC-
     SIFADDR ioctl.  The loopback interface should be the last
     interface configured, as protocols may use the order of con-
     figuration as an indication of priority.  The loopback
     should never be configured first unless no hardware inter-
     faces 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 inter-
     face automatically, using a nonstandard Internet address
     (127.1).  Use of that address is now discouraged; a reserved
     host address for the local network should be used instead.






















Printed 11/26/99	 August 1, 1987                         1