LO(4) BSD Programmer's Manual LO(4)NAMElo - software loopback network interface
SYNOPSIS
pseudo-device loop count
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 program ifconfig(8). The
loopback interface should be the last interface configured, as protocols
may use the order of configuration as an indication of priority. The
loopback interface should never be configured first unless no hardware
interfaces exist.
The loopback interface may be configured with any number of addresses,
this is frequently used for supporting virtual hosts. While not strictly
necessary, it is possible to define multiple loopback interfaces to fa-
cilitate the grouping of virtual addresses. This may be accomplishd by
specifying the count at kernel config time, modifying the nloif variable
in the system with bpatch(1) before booting, or by modifying the
net.link_layer.generic.lo.numif variable with sysctl(1).
NOTES
Previous versions of the system enabled the loopback interface automati-
cally, using a nonstandard Internet address (127.1). The address must
now be set at boot time. The address 127.1 may be used, as network 127
is now designated as the loopback network.
DIAGNOSTICS
lo%d: can't handle af%d. The interface was handed a message with ad-
dresses formatted in an unsuitable address family; the packet was
dropped.
SEE ALSOintro(4), inet(4), ns(4), ifconfig(8)HISTORY
The lo device appeared in 4.2BSD.
4.2 Berkeley Distribution June 5, 1993 1