bsd man page for lo

LO(4)							     Kernel Interfaces Manual							     LO(4)

NAME
       lo - software loopback network interface

SYNOPSIS
       /sys/conf/SYSTEM:
	    NLOOP     1    # loop-back pseudo-device

DESCRIPTION
       The  loop  interface is a software loopback mechanism which may be used for performance analysis, software testing, and/or local communica-
       tion.  As with other network interfaces, 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 SIOCSIFADDR ioctl.  The loopback interface should be the last interface con-
       figured, 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 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.

3rd Berkeley Distribution					  August 1, 1987							     LO(4)