lo - software loopback network interface
NLOOP 1 # loop-back pseudo-device
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 config-
ured first unless no hardware interfaces exist.
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 ALSOintro(4N), inet(4F), ns(4F)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.
3rd Berkeley Distribution August 1, 1987 LO(4)