LO(4) Kernel Interfaces Manual LO(4)
NAME
lo - software loopback network interface
SYNOPSIS
/sys/conf/SYSTEM:
NLOOP 1 # loop-back pseudo-device
DESCRIPTION
The loop interface is a software loopback mechanism which may be used for performance analysis, software testing, and/or local communica-
tion. 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 con-
figured, 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(4N), inet(4F), ns(4F)
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.
3rd Berkeley Distribution August 1, 1987 LO(4)