1.\" 2.\" Copyright (c) 2001 Yar Tikhiy 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd November 14, 2002 29.Dt VLAN 4 30.Os 31.Sh NAME 32.Nm vlan 33.Nd IEEE 802.1Q VLAN network interface 34.Sh SYNOPSIS 35.Cd device vlan 36.\" 37.Sh DESCRIPTION 38The 39.Nm 40driver demultiplexes frames tagged according to 41the IEEE 802.1Q standard into logical 42.Nm 43network interfaces, which allows routing/bridging between 44multiple VLANs through a single switch trunk port. 45.Pp 46Each 47.Nm 48interface is created at runtime using interface cloning. 49This is 50most easily done with the 51.Xr ifconfig 8 52.Cm create 53command or using the 54.Va cloned_interfaces 55variable in 56.Xr rc.conf 5 . 57.Pp 58To function, a 59.Nm 60interface must be assigned a parent interface and 61numeric VLAN tag using 62.Xr ifconfig 8 . 63A single parent can be assigned to multiple 64.Nm 65interfaces provided they have different tags. 66The parent interface is likely to be an ethernet card connected 67to a properly configured switch port. 68The VLAN tag should match one of those set up in the switched 69network. 70.Pp 71The 72.Nm 73driver supports physical devices that do 74the VLAN demultiplexing in firmware. 75Devices that have hardware support for 76802.1Q VLANs are automatically recognized by their interface capabilities. 77.\" 78.Ss "Selecting the Right Network Interface Card to Run VLANs Through" 79By now, the only NICs that have both hardware support and proper 80driver hooks for the 802.1Q VLAN technology in 81.Fx 82are 83.Xr bge 4 , 84.Xr em 4 , 85.Xr gx 4 , 86.Xr nge 4 , 87.Xr ti 4 , 88and 89.Xr txp 4 . 90.Pp 91The rest of the ethernet NICs supported by 92.Fx 93can run 94VLANs using software emulation in the 95.Nm 96driver. 97However, most of them lack the capability 98of transmitting and/or receiving oversized frames. 99Using such a NIC as a parent interface 100implies a reduced MTU on the corresponding 101.Nm 102interfaces. 103In the modern Internet, this is likely to cause 104.Xr tcp 4 105connectivity problems due to massive, inadequate 106.Xr icmp 4 107filtering that breaks the Path MTU Discovery mechanism. 108.Pp 109The NICs that support oversized frames are as follows: 110.Bl -tag -width ".Xr fxp 4 " -offset indent 111.It Xr dc 4 112supports long frames for 113.Nm 114natively. 115.It Xr de 4 116requires defining 117.Dv BIG_PACKET 118in the 119.Pa /usr/src/sys/pci/if_de.c 120source file and rebuilding the kernel 121or module. 122The hack works only for the 21041, 21140, and 21140A chips. 123.It Xr fxp 4 124supports long frames for 125.Nm 126natively. 127.It Xr sis 4 128supports long frames for 129.Nm 130natively. 131.It Xr ste 4 132supports long frames for 133.Nm 134natively. 135.It Xr tl 4 136has support for long frames. 137.It Xr tx 4 138supports long frames for 139.Nm 140natively. 141.It Xr xl 4 142supports long frames only if the card is built on a newer chip 143(Cyclone and above). 144.El 145.Pp 146The 147.Nm 148driver automatically recognizes devices that support oversized frames 149for 150.Nm 151use and calculates the appropriate frame MTU based on the 152capabilities of the parent interface. 153.Sh SEE ALSO 154.Xr ifconfig 8 155.Sh BUGS 156No 802.1Q features except VLAN tagging are implemented. 157