66 lines
1.5 KiB
Groff
66 lines
1.5 KiB
Groff
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.\"
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.\" $Id$
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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, FreeBSD supports bridging on ethernet-type
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interfaces. 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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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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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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Set to 1 to enable
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.Nm ipfw
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filtering on bridged packets. Note that
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.Nm ipfw
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rules only apply
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to IP packets. Non-IP packets are subject to the default
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.Nm ipfw
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rule (number 65535) 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. 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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Not all interface support bridging -- at the moment it works for
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``ed'', ``de'', ``ep'', ``fxp'', ``lnc'' interfaces.
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.Sh SEE ALSO
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.Xr ip 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 has been introduced in FreeBSD 2.2.8
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by Luigi Rizzo <luigi@iet.unipi.it>.
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