BRIDGE(4)                 NetBSD Programmer's Manual                 BRIDGE(4)

     bridge - network bridge device

     pseudo-device bridge

     The bridge driver creates a logical link between two or more IEEE 802
     networks that use the same (or ``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.

     To use bridge, the administrator must first create the interface and con-
     figure the bridge parameters.  The bridge is created using the
     ifconfig(8) `create' subcommand.  The learning and forwarding behavior
     and other parameters of a bridge are configured by the brconfig(8) utili-

     A bridge can be used to provide several services, such as a simple
     802.11-to-Ethernet bridge for wireless hosts, and traffic isolation.

     A bridge works like a hub, forwarding traffic from one interface to an-
     other.  Multicast and broadcast packets are always forwarded to all in-
     terfaces that are part of the bridge.  For unicast traffic, the bridge
     learns which MAC addresses are associated with which segments will for-
     ward the traffic selectively.

     The bridge driver implements the IEEE 802.1D Spanning Tree protocol
     (STP).  Spanning Tree is used to detect and remove loops in a network


     The bridge driver first appeared in NetBSD 1.6.

     The bridge driver was originally written by Jason L. Wright
     <> as part of an undergraduate independent study at the
     University of North Carolina at Greensboro.

     This version of the bridge driver has been heavily modified from the
     original version by
     Jason R. Thorpe <>.

     The bridge driver currently supports only Ethernet and Ethernet-like
     (e.g. 802.11) network devices.

     The bridge driver currently does not support snooping via bpf(4) or
     transparent filtering.

NetBSD 1.6                      August 17, 2001                              1

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