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BRIDGE(4)              FreeBSD Kernel Interfaces Manual              BRIDGE(4)

NAME
     bridge - bridging support

SYNOPSIS
     options BRIDGE

DESCRIPTION
     FreeBSD supports bridging on Ethernet-type interfaces.

     Runtime operation of the bridge is controlled by several sysctl(8)
     variables.  The net.link.ether.bridge variable can be set to 1 to enable
     bridging, or set to 0 to disable it.

     The net.link.ether.bridge_ipfw variable can be set to 1 to enable ipfw(8)
     filtering on bridged packets.  Note that ipfw(8) rules only apply to IP
     packets.  Non-IP packets are subject to the default ipfw(8) rule (number
     65535) which must be an allow rule if ARP and other non-IP packets need
     to flow through the bridge.

     The bridge configuration is controlled by the net.link.ether.bridge_cfg
     variable.  It consists of a comma-separated list of interface:cluster
     pairs, where all interfaces with the same cluster number will be bridged
     together.

     Another variable reinitializes the bridge; this is required if bridged
     configurations include loadable interfaces.  After loading new interface
     drivers, setting the net.link.ether.bridge_refresh variable to 1 will
     cause the bridge to reinitialize itself.

EXAMPLES
     The following command will cause the ep0 and fxp0 interfaces to be
     bridged together, and the fxp1 and de0 interfaces to be bridged together:

           sysctl net.link.ether.bridge_cfg=ep0:0,fxp0:0,fxp1:1,de0:1

BUGS
     Care must be taken not to construct loops in the bridge topology.  The
     kernel supports only a primitive form of loop detection, by disabling
     some interfaces when a loop is detected.  No support for a daemon running
     the spanning tree algorithm is currently provided.

     With bridging active, interfaces are in promiscuous mode, thus causing
     some load on the system to receive and filter out undesired traffic.

     Extended functionality to enable bridging selectively on clusters of
     interfaces is still in the works.

     Interfaces that cannot be put into promiscuous mode or that don't support
     sending packets with arbitrary Ethernet source addresses are not
     compatible with bridging.

SEE ALSO
     ip(4), ng_bridge(4), ipfw(8), sysctl(8)

HISTORY
     bridge bridging was introduced in FreeBSD 2.2.8 by Luigi Rizzo
     <luigi@iet.unipi.it>.

FreeBSD 11.0-PRERELEASE       September 28, 1998       FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | BUGS | SEE ALSO | HISTORY

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