111 lines
3.8 KiB
Groff
111 lines
3.8 KiB
Groff
.\" $NetBSD: bridge.4,v 1.4 2002/06/08 23:21:36 itojun Exp $
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.\"
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.\" Copyright 2001 Wasabi Systems, Inc.
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.\" All rights reserved.
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.\"
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.\" Written by Jason R. Thorpe for Wasabi Systems, Inc.
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed for the NetBSD Project by
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.\" Wasabi Systems, Inc.
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.\" 4. The name of Wasabi Systems, Inc. may not be used to endorse
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.\" or promote products derived from this software without specific prior
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.\" written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd August 17, 2001
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.Dt BRIDGE 4
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.Os
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.Sh NAME
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.Nm bridge
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.Nd network bridge device
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.Sh SYNOPSIS
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.Cd "pseudo-device bridge"
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.Sh DESCRIPTION
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The
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.Nm
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driver creates a logical link between two or more IEEE 802 networks
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that use the same (or
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.Dq similar enough )
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framing format. For example, it is possible to bridge Ethernet and
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802.11 networks together, but it is not possible to bridge Ethernet
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and Token Ring together.
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.Pp
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To use
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.Nm bridge ,
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the administrator must first create the interface and configure
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the bridge parameters. The bridge is created using the
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.Xr ifconfig 8
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.Sq create
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subcommand.
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The learning and forwarding behavior and other parameters of a
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bridge are configured by the
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.Xr brconfig 8
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utility.
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.Pp
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A bridge can be used to provide several services, such as a simple
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802.11-to-Ethernet bridge for wireless hosts, and traffic isolation.
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.Pp
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A bridge works like a hub, forwarding traffic from one interface
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to another. Multicast and broadcast packets are always forwarded
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to all interfaces that are part of the bridge. For unicast traffic,
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the bridge learns which MAC addresses are associated with which segments
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will forward the traffic selectively.
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.Pp
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The
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.Nm
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driver implements the IEEE 802.1D Spanning Tree protocol (STP). Spanning
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Tree is used to detect and remove loops in a network topology.
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.Sh SEE ALSO
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.Xr brconfig 8
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Nx 1.6 .
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.Sh AUTHORS
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The
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.Nm bridge
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driver was originally written by
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.An Jason L. Wright
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.Aq jason@thought.net
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as part of an undergraduate independent study at the University of
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North Carolina at Greensboro.
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.Pp
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This version of the
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.Nm
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driver has been heavily modified from the original version by
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.An Jason R. Thorpe
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.Aq thorpej@wasabisystems.com .
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.Sh BUGS
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The
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.Nm
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driver currently supports only Ethernet and Ethernet-like (e.g. 802.11)
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network devices, with exactly the same interface MTU size as the bridge device.
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.Pp
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The
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.Nm
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driver currently does not support snooping via
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.Xr bpf 4
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or transparent filtering.
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