|
NAME | SYNOPSIS | DESCRIPTION | INSTANCES | PORTS | AGEING | SPANNING TREE PROTOCOL | NOTES | SEE ALSO | AUTHOR | COLOPHON |
|
BRCTL(8) BRCTL(8)
brctl - ethernet bridge administration
brctl [command]
brctl is used to set up, maintain, and inspect the ethernet bridge
configuration in the Linux kernel.
An ethernet bridge is a device commonly used to connect different
networks of ethernets together, so that these ethernets will appear
as one ethernet to the participants.
Each of the ethernets being connected corresponds to one physical
interface in the bridge. These individual ethernets are bundled into
one bigger ('logical') ethernet, this bigger ethernet corresponds to
the bridge network interface.
The command brctl addbr <name> creates a new instance of the ethernet
bridge. The network interface corresponding to the bridge will be
called <name>.
The command brctl delbr <name> deletes the instance <name> of the
ethernet bridge. The network interface corresponding to the bridge
must be down before it can be deleted!
The command brctl show shows all current instances of the ethernet
bridge.
Each bridge has a number of ports attached to it. Network traffic
coming in on any of these ports will be forwarded to the other ports
transparently, so that the bridge is invisible to the rest of the
network (i.e. it will not show up in traceroute(8) ).
The command brctl addif <brname> <ifname> will make the interface
<ifname> a port of the bridge <brname>. This means that all frames
received on <ifname> will be processed as if destined for the bridge.
Also, when sending frames on <brname>, <ifname> will be considered as
a potential output interface.
The command brctl delif <brname> <ifname> will detach the interface
<ifname> from the bridge <brname>.
The command brctl show <brname> will show some information on the
bridge and its attached ports.
The bridge keeps track of ethernet addresses seen on each port. When
it needs to forward a frame, and it happens to know on which port the
destination ethernet address (specified in the frame) is located, it
can 'cheat' by forwarding the frame to that port only, thus saving a
lot of redundant copies and transmits.
However, the ethernet address location data is not static data.
Machines can move to other ports, network cards can be replaced
(which changes the machine's ethernet address), etc.
brctl showmacs <brname> shows a list of learned MAC addresses for
this bridge.
brctl setageing <brname> <time> sets the ethernet (MAC) address
ageing time, in seconds. After <time> seconds of not having seen a
frame coming from a certain address, the bridge will time out
(delete) that address from the Forwarding DataBase (fdb).
brctl setgcint <brname> <time> sets the garbage collection interval
for the bridge <brname> to <time> seconds. This means that the bridge
will check the forwarding database for timed out entries every <time>
seconds.
Multiple ethernet bridges can work together to create even larger
networks of ethernets using the IEEE 802.1d spanning tree protocol.
This protocol is used for finding the shortest path between two
ethernets, and for eliminating loops from the topology. As this
protocol is a standard, Linux bridges will interwork properly with
other third party bridge products. Bridges communicate with each
other by sending and receiving BPDUs (Bridge Protocol Data Units).
These BPDUs can be recognised by an ethernet destination address of
01:80:c2:00:00:00.
The spanning tree protocol can also be turned off (for those
situations where it just doesn't make sense, for example when this
Linux box is the only bridge on the LAN, or when you know that there
are no loops in the topology.)
brctl(8) can be used for configuring certain spanning tree protocol
parameters. For an explanation of these parameters, see the IEEE
802.1d specification (or send me an email). The default values should
be just fine. If you don't know what these parameters mean, you
probably won't feel the desire to tweak them.
brctl stp <bridge> <state> controls this bridge instance's
participation in the spanning tree protocol. If <state> is "on" or
"yes" the STP will be turned on, otherwise it will be turned off.
When turned off, the bridge will not send or receive BPDUs, and will
thus not participate in the spanning tree protocol. If your bridge
isn't the only bridge on the LAN, or if there are loops in the LAN's
topology, DO NOT turn this option off. If you turn this option off,
please know what you are doing.
brctl setbridgeprio <bridge> <priority> sets the bridge's priority to
<priority>. The priority value is an unsigned 16-bit quantity (a
number between 0 and 65535), and has no dimension. Lower priority
values are 'better'. The bridge with the lowest priority will be
elected 'root bridge'.
brctl setfd <bridge> <time> sets the bridge's 'bridge forward delay'
to <time> seconds.
brctl sethello <bridge> <time> sets the bridge's 'bridge hello time'
to <time> seconds.
brctl setmaxage <bridge> <time> sets the bridge's 'maximum message
age' to <time> seconds.
brctl setpathcost <bridge> <port> <cost> sets the port cost of the
port <port> to <cost>. This is a dimensionless metric.
brctl setportprio <bridge> <port> <priority> sets the port <port>'s
priority to <priority>. The priority value is an unsigned 8-bit
quantity (a number between 0 and 255), and has no dimension. This
metric is used in the designated port and root port selection
algorithms.
brctl(8) is obsolete. Some features such as STP guard, harpin mode,
fastleave and root block are intentionally not implemented in this
command. Instead use bridge command from iproute2 package for a more
full set of features.
iptables(8)
Lennert Buytenhek <buytenh@gnu.org> Stephen Hemminger
<stephen@networkplumber.org>
This page is part of the bridge-utils (Ethernet bridge utilities)
project. Information about the project can be found at
⟨https://wiki.linuxfoundation.org/networking/bridge⟩. If you have a
bug report for this manual page, send it to bridge@osdl.org. This
page was obtained from the project's upstream Git repository
⟨git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/bridge-utils.git⟩
on 2018-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2017-07-17.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
November 7, 2001 BRCTL(8)
Pages that refer to this page: network_namespaces(7), brctl(8)
|
HTML rendering created 2018-02-02 by Michael Kerrisk, author of The Linux Programming Interface, maintainer of the Linux man-pages project. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.
|
|