.\"	$NetBSD: brconfig.8,v 1.20 2020/07/19 14:43:35 wiz Exp $
.\"
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.\" Written by Jason R. Thorpe for Wasabi Systems, Inc.
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.Dd July 19, 2020
.Dt BRCONFIG 8
.Os
.Sh NAME
.Nm brconfig
.Nd configure network bridge parameters
.Sh SYNOPSIS
.Nm
.Fl a
.Nm
.Ar bridge
.Nm
.Ar bridge
.Ar command
.Op Ar args ...
.Sh DESCRIPTION
The
.Nm
utility is used to configure network bridge parameters and retrieve
network bridge parameters and status from the kernel.
The bridging function is implemented by the
.Xr bridge 4
driver.
.Pp
A network bridge 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
Bridge interfaces are created using the
.Xr ifconfig 8
command's
.Dq create
sub-command.
All other bridge configuration is performed using
.Nm .
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl a
Display the status of all bridge devices present on the system.
This flag is mutually exclusive with all other sub-commands.
.El
.Pp
All other operations require that a bridge be specified.
If a bridge is specified with no sub-commands,
the status of that bridge is displayed.
The following sub-commands are available:
.Bl -tag -width indent
.It Cm up
Start forwarding packets on the bridge.
.It Cm down
Stop forwarding packets on the bridge.
.It Cm add Ar interface
Add the interface named by
.Ar interface
as a member of the bridge.
The interface is put into promiscuous mode
so that it can receive every packet sent on the network.
.It Cm delete Ar interface
Remove the interface named by
.Ar interface
from the bridge.
Promiscuous mode is disabled on the interface when
it is removed from the bridge.
.It Cm addr
Display the addresses that have been learned by the bridge.
.It Cm maxaddr Ar size
Set the size of the bridge address cache to
.Ar size .
The default is 100 entries.
.It Cm timeout Ar seconds
Set the timeout of address cache entries to
.Ar seconds
seconds.
If
.Ar seconds
is zero, then address cache entries will not be expired.
The default is 1200 seconds.
.It Cm deladdr Ar address
Delete
.Ar address
from the address cache.
.It Cm flush
Delete all dynamically-learned addresses from the address cache.
.It Cm flushall
Delete all addresses, including static addresses, from the address cache.
.It Cm discover Ar interface
Mark an interface as a
.Dq discovering
interface.
When the bridge has no address cache entry
(either dynamic or static)
for the destination address of a packet,
the bridge will forward the packet to all
member interfaces marked as
.Dq discovering .
This is the default for all interfaces added to a bridge.
.It Cm -discover Ar interface
Clear the
.Dq discovering
attribute on a member interface.
For packets without the
.Dq discovering
attribute, the only packets forwarded on the interface are broadcast
or multicast packets and packets for which the destination address
is known to be on the interface's segment.
.It Cm ipf
Enable packet filtering with
.Xr pfil 9
on the bridge.
The current implementation passes
all ARP and RARP packets through the bridge
while filtering IP and IPv6 packets through the configured packet
filter, such as
.Xr npf 7 .
Other packet types are blocked.
.It Cm learn Ar interface
Mark an interface as a
.Dq learning
interface.
When a packet arrives on such an interface, the source
address of the packet is entered into the address cache as being a
destination address on the interface's segment.
This is the default for all interfaces added to a bridge.
.It Cm -learn Ar interface
Clear the
.Dq learning
attribute on a member interface.
.It Cm static Ar interface address
Add a static entry into the address cache pointing to
.Ar interface .
Static entries are never aged out of the cache or replaced, even if the address
is seen on a different interface.
.It Cm stp Ar interface
Enable Spanning Tree protocol on
.Ar interface .
The
.Xr bridge 4
driver has support for the IEEE 802.1D Spanning Tree protocol (STP).
Spanning Tree is used to detect and remove loops in a network topology.
.It Cm -stp Ar interface
Disable Spanning Tree protocol on
.Ar interface .
This is the default for all interfaces added to a bridge.
.It Cm maxage Ar seconds
Set the time that a Spanning Tree protocol configuration is valid.
The default is 20 seconds.
The minimum is 1 second and the maximum is 255 seconds.
.It Cm fwddelay Ar seconds
Set the time that must pass before an interface begins forwarding
packets when Spanning Tree is enabled.
The default is 15 seconds.
The minimum is 1 second and the maximum is 255 seconds.
.It Cm hellotime Ar seconds
Set the time between broadcasting of Spanning Tree protocol
configuration messages.
The default is 2 seconds.
The minimum is 1 second and the maximum is 255 seconds.
.It Cm priority Ar value
Set the bridge priority for Spanning Tree.
The default is 32768.
Allowed numerical values range from 0 (highest priority) to 65535
(lowest priority).
.It Cm ifpriority Ar interface Ar value
Set the Spanning Tree priority of
.Ar interface
to
.Ar value .
The default is 128.
The minimum is 0 and the maximum is 255.
.It Cm ifpathcost Ar interface Ar value
Set the Spanning Tree path cost of
.Ar interface
to
.Ar value .
The default is 55.
The minimum is 0 and the maximum is 65535.
.El
.Sh EXAMPLES
The following, when placed in the file
.Pa /etc/ifconfig.bridge0 ,
will cause a bridge called
.Sq bridge0
to be created, add the interfaces
.Sq ray0
and
.Sq fxp0
to the bridge, and then enable packet forwarding.
Such a configuration could be used to implement a simple
802.11-to-Ethernet bridge (assuming the 802.11 interface is
in ad-hoc mode).
.Bd -literal -offset indent
create
!brconfig $int add ray0 add fxp0 up
.Ed
.Pp
Consider a system with two 4-port Ethernet boards.
The following placed in the file
.Pa /etc/ifconfig.bridge0
will cause a bridge consisting of all 8 ports with Spanning Tree
enabled to be created:
.Bd -literal -offset indent
create
!brconfig $int \e
    add tlp0 stp tlp0 \e
    add tlp1 stp tlp1 \e
    add tlp2 stp tlp2 \e
    add tlp3 stp tlp3 \e
    add tlp4 stp tlp4 \e
    add tlp5 stp tlp5 \e
    add tlp6 stp tlp6 \e
    add tlp7 stp tlp7 \e
    up
.Ed
.Sh SEE ALSO
.Xr bridge 4 ,
.Xr pf 4 ,
.Xr ifconfig.if 5 ,
.Xr npf 7 ,
.Xr ifconfig 8 ,
.Xr pfil 9
.Sh HISTORY
The
.Nm
utility first appeared in
.Nx 1.6 .
.Sh AUTHORS
The
.Xr bridge 4
driver and
.Nm
utility were 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
utility was written from scratch by
.An Jason R. Thorpe
.Aq thorpej@wasabisystems.com .