NAME
lo —
software loopback network
interface
SYNOPSIS
pseudo-device loop
DESCRIPTION
Theloop 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(2). 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.
The loopback interface lo0 is created at
boottime, it always exists and cannot be destroyed with
ifconfig(8). Additional loopback interfaces can be created by using
the ifconfig(8) create command.
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
HISTORY
The lo device appeared in
4.2BSD.
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.