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. 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 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
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(4), inet(4), ns(4)*

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.

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* Not currently supported under MachTen