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.Dd March 18, 2015 29.Dt EPAIR 4 30.Os 31.Sh NAME 32.Nm epair 33.Nd A pair of virtual back-to-back connected Ethernet interfaces 34.Sh SYNOPSIS 35To compile this driver into the kernel, 36place the following line in your 37kernel configuration file: 38.Bd -ragged -offset indent 39.Cd "device epair" 40.Ed 41.Pp 42Alternatively, to load the driver as a 43module at boot time, place the following line in 44.Xr loader.conf 5 : 45.Bd -literal -offset indent 46if_epair_load="YES" 47.Ed 48.Sh DESCRIPTION 49The 50.Nm 51is a pair of Ethernet-like software interfaces, 52which are connected back-to-back with a virtual cross-over cable. 53.Pp 54Each 55.Nm 56interface pair is created at runtime using interface cloning. 57This is most easily done with the 58.Xr ifconfig 8 59.Cm create 60command or using the 61.Va cloned_interfaces 62variable in 63.Xr rc.conf 5 . 64While for cloning you only give either 65.Pa epair 66or 67.Pa epair<n> 68the 69.Nm 70pair will be named like 71.Pa epair<n>[ab] . 72This means the names of the first 73.Nm 74interfaces will be 75.Pa epair0a 76and 77.Pa epair0b . 78.Pp 79Like any other Ethernet interface, an 80.Nm 81needs to have a network address. 82Each 83.Nm 84will be assigned a locally administered address by default, 85that is only guaranteed to be unique within one network stack. 86To change the default addresses one may use the SIOCSIFADDR ioctl(2) or 87ifconfig(8) utility. 88.Pp 89The basic intent is to provide connectivity between two virtual 90network stack instances. 91When connected to an 92.Xr if_bridge 4 , 93one end of the interface pair can also be part of another (virtual) LAN. 94As with any other Ethernet interface, 95.Nm epair 96can have a 97.Xr vlan 4 98configured on top of it. 99.Sh SEE ALSO 100.Xr ioctl 2 , 101.Xr altq 4 , 102.Xr bpf 4 , 103.Xr if_bridge 4 , 104.Xr vlan 4 , 105.Xr loader.conf 5 , 106.Xr rc.conf 5 , 107.Xr ifconfig 8 108.Sh HISTORY 109The 110.Nm 111interface first appeared in 112.Fx 8.0 . 113.Sh AUTHORS 114The 115.Nm 116interface was written by 117.An Bjoern A. Zeeb, CK Software GmbH, 118under sponsorship from the FreeBSD Foundation. 119