1.\"- 2.\" Copyright (c) 2008 The FreeBSD Foundation 3.\" 4.\" This software was developed by CK Software GmbH under sponsorship 5.\" from the FreeBSD Foundation. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" $FreeBSD$ 29.\" 30.Dd March 18, 2015 31.Dt EPAIR 4 32.Os 33.Sh NAME 34.Nm epair 35.Nd A pair of virtual back-to-back connected Ethernet interfaces 36.Sh SYNOPSIS 37To compile this driver into the kernel, 38place the following line in your 39kernel configuration file: 40.Bd -ragged -offset indent 41.Cd "device epair" 42.Ed 43.Pp 44Alternatively, to load the driver as a 45module at boot time, place the following line in 46.Xr loader.conf 5 : 47.Bd -literal -offset indent 48if_epair_load="YES" 49.Ed 50.Sh DESCRIPTION 51The 52.Nm 53is a pair of Ethernet-like software interfaces, 54which are connected back-to-back with a virtual cross-over cable. 55.Pp 56Each 57.Nm 58interface pair is created at runtime using interface cloning. 59This is most easily done with the 60.Xr ifconfig 8 61.Cm create 62command or using the 63.Va cloned_interfaces 64variable in 65.Xr rc.conf 5 . 66While for cloning you only give either 67.Pa epair 68or 69.Pa epair<n> 70the 71.Nm 72pair will be named like 73.Pa epair<n>[ab] . 74This means the names of the first 75.Nm 76interfaces will be 77.Pa epair0a 78and 79.Pa epair0b . 80.Pp 81Like any other Ethernet interface, an 82.Nm 83needs to have a network address. 84Each 85.Nm 86will be assigned a locally administered address by default, 87that is only guaranteed to be unique within one network stack. 88To change the default addresses one may use the SIOCSIFADDR ioctl(2) or 89ifconfig(8) utility. 90.Pp 91The basic intent is to provide connectivity between two virtual 92network stack instances. 93When connected to an 94.Xr if_bridge 4 , 95one end of the interface pair can also be part of another (virtual) LAN. 96As with any other Ethernet interface, 97.Nm epair 98can have a 99.Xr vlan 4 100configured on top of it. 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