1.\"- 2.\" Copyright (c) 2008 The FreeBSD Foundation 3.\" All rights reserved. 4.\" 5.\" This software was developed by CK Software GmbH under sponsorship 6.\" from the FreeBSD Foundation. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.\" $FreeBSD$ 30.\" 31.Dd July 26, 2009 32.Dt EPAIR 4 33.Os 34.Sh NAME 35.Nm epair 36.Nd A pair of virtual back-to-back connected Ethernet interfaces. 37.Sh SYNOPSIS 38To compile this driver into the kernel, 39place the following line in your 40kernel configuration file: 41.Bd -ragged -offset indent 42.Cd "device epair" 43.Ed 44.Pp 45Alternatively, to load the driver as a 46module at boot time, place the following line in 47.Xr loader.conf 5 : 48.Bd -literal -offset indent 49if_epair_load="YES" 50.Ed 51.Sh DESCRIPTION 52The 53.Nm 54is a pair of Ethernet-like software interfaces, 55which are connected back-to-back with a virtual cross-over cable. 56.Pp 57Each 58.Nm 59interface pair is created at runtime using interface cloning. 60This is most easily done with the 61.Xr ifconfig 8 62.Cm create 63command or using the 64.Va cloned_interfaces 65variable in 66.Xr rc.conf 5 . 67While for cloning you only give either 68.Pa epair 69or 70.Pa epair<n> 71the 72.Nm 73pair will be named like 74.Pa epair<n>[ab] . 75This means the names of the first 76.Nm 77interfaces will be 78.Pa epair0a 79and 80.Pa epair0b . 81.Pp 82Like any other Ethernet interface, an 83.Nm 84needs to have a network address. 85Each 86.Nm 87will be assigned a locally administered address by default, 88that is only guaranteed to be unique within one network stack. 89To change the default addresses one may use the SIOCSIFADDR ioctl(2) or 90ifconfig(8) utility. 91.Pp 92The basic intend is to provide connectivity between two virtual 93network stack instances. 94When connected to a 95.Xr if_bridge 4 96one end of the interface pair can also be part of another (virtual) LAN. 97As with any other Ethernet interface one can configure 98.Xr vlan 4 99support on top of it. 100.Pp 101.Sh SEE ALSO 102.Xr ioctl 2 , 103.Xr altq 4 , 104.Xr bpf 4 , 105.Xr if_bridge 4 , 106.Xr vlan 4 , 107.Xr loader.conf 5 , 108.Xr rc.conf 5 , 109.Xr ifconfig 8 110.Sh HISTORY 111The 112.Nm 113interface first appeared in 114.Fx 8.0 . 115.Sh AUTHORS 116The 117.Nm 118interface was written by 119.An Bjoern A. Zeeb, CK Software GmbH, 120under sponsorship from the FreeBSD Foundation. 121