.\" Copyright (c) 1983 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)lo.4	6.2 (Berkeley) 05/16/86
.\"
.TH LO 4 ""
.UC 5
.SH NAME
lo \- software loopback network interface
.SH SYNOPSIS
.B pseudo-device loop
.SH DESCRIPTION
The
.I loop
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
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.
.SH DIAGNOSTICS
\fBlo%d: can't handle af%d\fP.  The interface was handed
a message with addresses formatted in an unsuitable address
family; the packet was dropped.
.SH SEE ALSO
intro(4N), inet(4F), ns(4F)
.SH BUGS
Previous versions of the system enabled the loopback interface
automatically, using a nonstandard Internet address (127.1).