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@(#)lo.4 8.1 (Berkeley) 6/5/93
.Dd $Mdocdate: June 2 2013 $ .Dt LO 4 .Os .Sh NAME .Nm lo .Nd software loopback network interface .Sh SYNOPSIS .Cd "pseudo-device loop" .Sh DESCRIPTION The .Nm loop interface is a software loopback mechanism which may be used for performance analysis, software testing, and/or local communication.
p A .Nm loop interface can be created at runtime using the c ifconfig lo Ns Ar N Ic create command or by setting up a .Xr hostname.if 5 configuration file for .Xr netstart 8 . The .Nm lo0 interface will always exist and cannot be destroyed using .Xr ifconfig 8 .
p 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 .Dv SIOCSIFADDR .Xr ioctl 2 . .Sh DIAGNOSTICS l -diag t lo0: can't handle afX. The interface was handed a message with addresses formatted in an unsuitable address family; the packet was dropped. .El .Sh SEE ALSO .Xr inet 4 , .Xr inet6 4 , .Xr netintro 4 , .Xr hostname.if 5 , .Xr ifconfig 8 , .Xr netstart 8 .Sh HISTORY The .Nm device appeared in x 4.2 .