NAME
lo —
software loopback network
interface
SYNOPSIS
pseudo-device loop
DESCRIPTION
The loop interface is a software loopback
mechanism which may be used for performance analysis, software testing,
and/or local communication.
A loop interface can be created at runtime
using the ifconfig loN
create command or by setting up a
hostname.if(5) configuration file for
netstart(8). The lo0 interface will always
exist and cannot be destroyed using
ifconfig(8).
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.
DIAGNOSTICS
- lo0: can't handle afX.
- The interface was handed a message with addresses formatted in an unsuitable address family; the packet was dropped.
SEE ALSO
inet(4), inet6(4), netintro(4), hostname.if(5), ifconfig(8), netstart(8)
HISTORY
The lo device appeared in
4.2BSD.
BUGS
Previous versions of the system enabled the loopback interface automatically, using a non-standard Internet address (127.1). Use of that address is now discouraged; a reserved host address for the local network should be used instead.