129 lines
4.4 KiB
Groff
129 lines
4.4 KiB
Groff
.\" $NetBSD: bridge.4,v 1.5 2004/01/31 20:14:11 jdc Exp $
|
|
.\"
|
|
.\" Copyright 2001 Wasabi Systems, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Written by Jason R. Thorpe for Wasabi Systems, Inc.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed for the NetBSD Project by
|
|
.\" Wasabi Systems, Inc.
|
|
.\" 4. The name of Wasabi Systems, Inc. may not be used to endorse
|
|
.\" or promote products derived from this software without specific prior
|
|
.\" written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd January 4, 2004
|
|
.Dt BRIDGE 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm bridge
|
|
.Nd network bridge device
|
|
.Sh SYNOPSIS
|
|
.Cd "pseudo-device bridge"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
driver creates a logical link between two or more IEEE 802 networks
|
|
that use the same (or
|
|
.Dq similar enough )
|
|
framing format.
|
|
For example, it is possible to bridge Ethernet and 802.11 networks together,
|
|
but it is not possible to bridge Ethernet and Token Ring together.
|
|
.Pp
|
|
To use
|
|
.Nm bridge ,
|
|
the administrator must first create the interface and configure
|
|
the bridge parameters.
|
|
The bridge is created using the
|
|
.Xr ifconfig 8
|
|
.Sq create
|
|
subcommand.
|
|
The learning and forwarding behavior and other parameters of a
|
|
bridge are configured by the
|
|
.Xr brconfig 8
|
|
utility.
|
|
.Pp
|
|
A bridge can be used to provide several services, such as a simple
|
|
802.11-to-Ethernet bridge for wireless hosts, and traffic isolation.
|
|
.Pp
|
|
A bridge works like a hub, forwarding traffic from one interface
|
|
to another.
|
|
Multicast and broadcast packets are always forwarded to all
|
|
interfaces that are part of the bridge.
|
|
For unicast traffic, the bridge learns which MAC addresses are associated
|
|
with which interfaces and will forward the traffic selectively.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver implements the IEEE 802.1D Spanning Tree protocol (STP).
|
|
Spanning Tree is used to detect and remove loops in a network topology.
|
|
.Pp
|
|
Transparent filtering for IP and IPv6 packets can be added with the kernel
|
|
configuration option
|
|
.Cd options BRIDGE_IPF .
|
|
.Pp
|
|
When filtering is enabled, bridged packets will pass through the filter
|
|
inbound on the originating interface and outbound on the appropriate
|
|
interfaces.
|
|
ARP and REVARP packets are forwarded without being filtered and others
|
|
that are not IP nor IPv6 packets are not forwarded when filtering is
|
|
enabled.
|
|
.Pp
|
|
Note that packets to and from the bridging host will be seen by the
|
|
filter on the interface with the appropriate address configured as well
|
|
as on the interface on which the packet arrives or departs.
|
|
.Sh SEE ALSO
|
|
.Xr options 4 ,
|
|
.Xr brconfig 8 ,
|
|
.Xr ipf 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
driver first appeared in
|
|
.Nx 1.6 .
|
|
.Sh AUTHORS
|
|
The
|
|
.Nm bridge
|
|
driver was originally written by
|
|
.An Jason L. Wright
|
|
.Aq jason@thought.net
|
|
as part of an undergraduate independent study at the University of
|
|
North Carolina at Greensboro.
|
|
.Pp
|
|
This version of the
|
|
.Nm
|
|
driver has been heavily modified from the original version by
|
|
.An Jason R. Thorpe
|
|
.Aq thorpej@wasabisystems.com .
|
|
.Sh BUGS
|
|
The
|
|
.Nm
|
|
driver currently supports only Ethernet and Ethernet-like (e.g. 802.11)
|
|
network devices, with exactly the same interface MTU size as the bridge device.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver currently does not support snooping via
|
|
.Xr bpf 4 .
|