76 lines
1.6 KiB
Groff
76 lines
1.6 KiB
Groff
.\"
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.\" $FreeBSD$
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.\"
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.Dd Sep 28, 1998
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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 Bridging support
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.Sh DESCRIPTION
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Starting from version 2.2.8,
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.Fx
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supports bridging on ethernet-type
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interfaces.
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This is achieved using the following option
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.Bd -literal
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options BRIDGE
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.Ed
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.Pp
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in the kernel config file, and is controlled by two
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.Nm sysctl
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variables:
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.Bd -literal
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net.link.ether.bridge
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.Ed
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.Pp
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Set to 1 to enable bridging, set to 0 to disable it
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.Bd -literal
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net.link.ether.bridge_ipfw
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.Ed
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.Pp
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Set to 1 to enable
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.Nm ipfw
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filtering on bridged packets.
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Note that
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.Nm ipfw
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rules only apply
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to IP packets.
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Non-IP packets are subject to the default
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.Nm ipfw
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rule
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.Pq number 65535
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which must be an
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.Ar allow
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rule if we want ARP and other non-IP packets to flow through the
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bridge.
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.Sh BUGS
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.Pp
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Care must be taken not to construct loops in the bridge topology.
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The kernel supports only a primitive form of loop detection, by disabling
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some interfaces when a loop is detected.
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No support for a daemon running the
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spanning tree algorithm is currently provided.
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.Pp
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With bridging active, interfaces are in promiscuous mode,
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thus causing some load on the system to receive and filter
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out undesired traffic.
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.Pp
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Extended functionality to enable bridging selectively on clusters
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of interfaces is still in the works.
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.Pp
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Interfaces that cannot be put into promiscuous mode or that don't
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support sending packets with arbitrary Ethernet source addresses
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are not compatible with bridging.
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.Sh SEE ALSO
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.Xr ip 4 ,
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.Xr ng_bridge 4 ,
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.Xr ipfw 8 ,
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.Xr sysctl 8
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.Sh HISTORY
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.Nm
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bridging was introduced in
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.Fx 2.2.8
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by
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.An Luigi Rizzo Aq luigi@iet.unipi.it .
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