db40c1aef4
One to notify the system that the MTU for VLAN can be 1500 so the vlan will automatically be configured with a 1500 MTU the other is to ignore the error case if the received frame is to long. The frame size notification came from code in the SIS driver, and the support for long frames derived from the NetBSD Tulip driver. Tested on: 4 port D-Link adapter DFE-570TX 4 Intel 21143 Netgear card with 82c169 PNIC 10/100BaseTX Reviewed by: ru (manpage), wpaul (not objected to), archie Approved by: imp Obtained from: NetBSD
156 lines
4.1 KiB
Groff
156 lines
4.1 KiB
Groff
.\"
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.\" Copyright (c) 2001 Yar Tikhiy
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 25, 2001
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.Dt VLAN 4
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.Os
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.Sh NAME
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.Nm vlan
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.Nd IEEE 802.1Q VLAN network interface
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.Sh SYNOPSIS
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.Cd device vlan
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.\"
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.Sh DESCRIPTION
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The
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.Nm
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driver demultiplexes frames tagged according to
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the IEEE 802.1Q standard into logical
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.Nm
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network interfaces, which allows routing/bridging between
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multiple VLANs through a single switch trunk port.
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.Pp
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To function, a
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.Nm
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interface must be assigned a parent interface and
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numeric VLAN tag using
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.Xr ifconfig 8 .
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A single parent can be assigned to multiple
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.Nm
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interfaces provided they have different tags.
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The parent interface is likely to be an ethernet card connected
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to a properly configured switch port.
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The VLAN tag should match one of those set up in the switched
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network.
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.Pp
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The
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.Nm
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driver supports physical devices that do
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the VLAN demultiplexing in firmware.
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The
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.Cm link0
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flag should be set on a
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.Nm
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interface
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.Pq Em not on its parent
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using
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.Xr ifconfig 8
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in that case to indicate that the hardware support for
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the 802.1Q VLANs is present in its parent.
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.\"
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.Ss "Selecting the Right Network Interface Card to Run VLANs Through"
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By now, the only NICs that have both hardware support and proper
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driver hooks for the 802.1Q VLAN technology in
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.Fx
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are
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.Xr bge 4 ,
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.Xr nge 4 ,
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.Xr ti 4 ,
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and
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.Xr txp 4 .
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.Pp
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The rest of the ethernet NICs supported by
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.Fx
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can run
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VLANs using the software emulation in the
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.Nm
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driver.
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However, most of them lack the capability
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of transmitting and/or receiving oversized frames.
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Using such a NIC as a parent interface for a
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.Nm
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implies a reduced MTU on the corresponding
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.Nm
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interfaces.
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In the modern Internet, this is likely to cause
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.Xr tcp 4
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connectivity problems due to massive, inadequate
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.Xr icmp 4
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filtering that breaks the Path MTU Discovery mechanism.
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.Pp
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The NICs that support oversized frames are as follows:
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.Bl -tag -width ".Xr fxp 4 " -offset indent
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.It Xr dc 4
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supports long frames for the
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.Nm
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natively.
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.It Xr de 4
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requires defining
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.Dv BIG_PACKET
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in the
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.Pa /usr/src/sys/pci/if_de.c
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source file and rebuilding the kernel
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or module.
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The hack works only for the 21041, 21140, and 21140A chips.
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.It Xr fxp 4
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supports long frames for the
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.Nm
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natively.
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.It Xr sis 4
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supports long frames for the
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.Nm
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natively.
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.It Xr tl 4
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does support long frames.
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.It Xr tx 4
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does support long frames.
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.It Xr wx 4
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does support long frames.
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.It Xr xl 4
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supports long frames only if the card is built on a newer chip
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(Cyclone and above).
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.El
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.Pp
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Note:
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Except for
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.Xr fxp 4 ,
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.Xr sis 4
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and
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.Xr tx 4 ,
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none of the above drivers inform the
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.Nm
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driver about their support for long frames.
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Just fix the MTU of a
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.Nm
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interface if it appears to be lower than 1500 bytes after
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attaching the
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.Nm
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to a parent interface that is known to support long frames.
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.Sh SEE ALSO
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.Xr ifconfig 8
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.Sh BUGS
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No 802.1Q features except VLAN tagging are implemented.
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