2.11BSD/man/cat4/lo.0
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