BRIDGE(8) Linux BRIDGE(8)
bridge - show / manipulate bridge addresses and devices
bridge [ OPTIONS ] OBJECT { COMMAND | help }
OBJECT := { link | fdb | mdb | vlan | monitor }
OPTIONS := { -V[ersion] | -s[tatistics] | -n[etns] name | -b[atch]
filename | -c[lor] | -p[retty] | -j[son] | -o[neline] }
bridge link set dev DEV [ cost COST ] [ priority PRIO ] [ state
STATE ] [ guard { on | off } ] [ hairpin { on | off } ] [
fastleave { on | off } ] [ root_block { on | off } ] [
learning { on | off } ] [ learning_sync { on | off } ] [
flood { on | off } ] [ hwmode { vepa | veb } ] [ mcast_flood
{ on | off } ] [ mcast_to_unicast { on | off } ] [
neigh_suppress { on | off } ] [ vlan_tunnel { on | off } ] [
isolated { on | off } ] [ backup_port DEVICE ] [
nobackup_port ] [ self ] [ master ]
bridge link [ show ] [ dev DEV ]
bridge fdb { add | append | del | replace } LLADDR dev DEV { local |
static | dynamic } [ self ] [ master ] [ router ] [ use ] [
extern_learn ] [ sticky ] [ dst IPADDR ] [ src_vni VNI ] [
vni VNI ] [ port PORT ] [ via DEVICE ]
bridge fdb [ show ] [ dev DEV ] [ br BRDEV ] [ brport DEV ] [ vlan
VID ] [ state STATE ]
bridge fdb get LLADDR [ dev DEV ] [ br BRDEV ] [ vlan VID ] [ self ]
[ master ]
bridge mdb { add | del } dev DEV port PORT grp GROUP [ permanent |
temp ] [ vid VID ]
bridge mdb show [ dev DEV ]
bridge vlan { add | del } dev DEV vid VID [ tunnel_info TUNNEL_ID ] [
pvid ] [ untagged ] [ self ] [ master ]
bridge vlan [ show | tunnelshow ] [ dev DEV ]
bridge monitor [ all | neigh | link | mdb ]
-V, -Version
print the version of the bridge utility and exit.
-s, -stats, -statistics
output more information. If this option is given multiple
times, the amount of information increases. As a rule, the
information is statistics or some time values.
-d, -details
print detailed information about MDB router ports.
-n, -net, -netns <NETNS>
switches bridge to the specified network namespace NETNS.
Actually it just simplifies executing of:
ip netns exec NETNS bridge [ OPTIONS ] OBJECT { COMMAND | help
}
to
bridge -n[etns] NETNS [ OPTIONS ] OBJECT { COMMAND | help }
-b, -batch <FILENAME>
Read commands from provided file or standard input and invoke
them. First failure will cause termination of bridge command.
-force Don't terminate bridge command on errors in batch mode. If
there were any errors during execution of the commands, the
application return code will be non zero.
-c[color][={always|auto|never}
Configure color output. If parameter is omitted or always,
color output is enabled regardless of stdout state. If
parameter is auto, stdout is checked to be a terminal before
enabling color output. If parameter is never, color output is
disabled. If specified multiple times, the last one takes
precedence. This flag is ignored if -json is also given.
-j, -json
Output results in JavaScript Object Notation (JSON).
-p, -pretty
When combined with -j generate a pretty JSON output.
-o, -oneline
output each record on a single line, replacing line feeds with
the '\' character. This is convenient when you want to count
records with wc(1) or to grep(1) the output.
OBJECT
link - Bridge port.
fdb - Forwarding Database entry.
mdb - Multicast group database entry.
vlan - VLAN filter list.
COMMAND
Specifies the action to perform on the object. The set of possible
actions depends on the object type. As a rule, it is possible to
add, delete and show (or list ) objects, but some objects do not
allow all of these operations or have some additional commands. The
help command is available for all objects. It prints out a list of
available commands and argument syntax conventions.
If no command is given, some default command is assumed. Usually it
is list or, if the objects of this class cannot be listed, help.
link objects correspond to the port devices of the bridge.
The corresponding commands set and display port status and bridge
specific attributes.
bridge link set - set bridge specific attributes on a port
dev NAME
interface name of the bridge port
cost COST
the STP path cost of the specified port.
priority PRIO
the STP port priority. The priority value is an unsigned 8-bit
quantity (number between 0 and 255). This metric is used in
the designated port an droot port selection algorithms.
state STATE
the operation state of the port. Except state 0 (disable STP
or BPDU filter feature), this is primarily used by user space
STP/RSTP implementation. One may enter port state name (case
insensitive), or one of the numbers below. Negative inputs are
ignored, and unrecognized names return an error.
0 - port is in STP DISABLED state. Make this port completely
inactive for STP. This is also called BPDU filter and could be
used to disable STP on an untrusted port, like a leaf virtual
devices.
1 - port is in STP LISTENING state. Only valid if STP is
enabled on the bridge. In this state the port listens for STP
BPDUs and drops all other traffic frames.
2 - port is in STP LEARNING state. Only valid if STP is
enabled on the bridge. In this state the port will accept
traffic only for the purpose of updating MAC address tables.
3 - port is in STP FORWARDING state. Port is fully active.
4 - port is in STP BLOCKING state. Only valid if STP is
enabled on the bridge. This state is used during the STP
election process. In this state, port will only process STP
BPDUs.
guard on or guard off
Controls whether STP BPDUs will be processed by the bridge
port. By default, the flag is turned off allowed BPDU
processing. Turning this flag on will disables the bridge port
if a STP BPDU packet is received.
If running Spanning Tree on bridge, hostile devices on the
network may send BPDU on a port and cause network failure.
Setting guard on will detect and stop this by disabling the
port. The port will be restarted if link is brought down, or
removed and reattached. For example if guard is enable on
eth0:
ip link set dev eth0 down; ip link set dev eth0 up
hairpin on or hairpin off
Controls whether traffic may be send back out of the port on
which it was received. This option is also called reflective
relay mode, and is used to support basic VEPA (Virtual
Ethernet Port Aggregator) capabilities. By default, this flag
is turned off and the bridge will not forward traffic back out
of the receiving port.
fastleave on or fastleave off
This flag allows the bridge to immediately stop multicast
traffic on a port that receives IGMP Leave message. It is only
used with IGMP snooping is enabled on the bridge. By default
the flag is off.
root_block on or root_block off
Controls whether a given port is allowed to become root port
or not. Only used when STP is enabled on the bridge. By
default the flag is off.
This feature is also called root port guard. If BPDU is
received from a leaf (edge) port, it should not be elected as
root port. This could be used if using STP on a bridge and the
downstream bridges are not fully trusted; this prevents a
hostile guest from rerouting traffic.
learning on or learning off
Controls whether a given port will learn MAC addresses from
received traffic or not. If learning if off, the bridge will
end up flooding any traffic for which it has no FDB entry. By
default this flag is on.
learning_sync on or learning_sync off
Controls whether a given port will sync MAC addresses learned
on device port to bridge FDB.
flood on or flood off
Controls whether a given port will flood unicast traffic for
which there is no FDB entry. By default this flag is on.
hwmode Some network interface cards support HW bridge functionality
and they may be configured in different modes. Currently
support modes are:
vepa - Data sent between HW ports is sent on the wire to the
external switch.
veb - bridging happens in hardware.
mcast_flood on or mcast_flood off
Controls whether a given port will flood multicast traffic for
which there is no MDB entry. By default this flag is on.
mcast_to_unicast on or mcast_to_unicast off
Controls whether a given port will replicate packets using
unicast instead of multicast. By default this flag is off.
This is done by copying the packet per host and changing the
multicast destination MAC to a unicast one accordingly.
mcast_to_unicast works on top of the multicast snooping
feature of the bridge. Which means unicast copies are only
delivered to hosts which are interested in it and signalized
this via IGMP/MLD reports previously.
This feature is intended for interface types which have a more
reliable and/or efficient way to deliver unicast packets than
broadcast ones (e.g. WiFi).
However, it should only be enabled on interfaces where no
IGMPv2/MLDv1 report suppression takes place. IGMP/MLD report
suppression issue is usually overcome by the network daemon
(supplicant) enabling AP isolation and by that separating all
STAs.
Delivery of STA-to-STA IP multicast is made possible again by
enabling and utilizing the bridge hairpin mode, which
considers the incoming port as a potential outgoing port, too
(see hairpin option). Hairpin mode is performed after
multicast snooping, therefore leading to only deliver reports
to STAs running a multicast router.
neigh_suppress on or neigh_suppress off
Controls whether neigh discovery (arp and nd) proxy and
suppression is enabled on the port. By default this flag is
off.
vlan_tunnel on or vlan_tunnel off
Controls whether vlan to tunnel mapping is enabled on the
port. By default this flag is off.
isolated on or isolated off
Controls whether a given port will be isolated, which means it
will be able to communicate with non-isolated ports only. By
default this flag is off.
backup_port DEVICE
If the port loses carrier all traffic will be redirected to
the configured backup port
nobackup_port
Removes the currently configured backup port
self link setting is configured on specified physical device
master link setting is configured on the software bridge (default)
-t, -timestamp
display current time when using monitor option.
bridge link show - list ports configuration for all bridges.
This command displays port configuration and flags for all bridges.
To display port configuration and flags for a specific bridge, use
the "ip link show master <bridge_device>" command.
fdb objects contain known Ethernet addresses on a link.
The corresponding commands display fdb entries, add new entries,
append entries, and delete old ones.
bridge fdb add - add a new fdb entry
This command creates a new fdb entry.
LLADDR the Ethernet MAC address.
dev DEV
the interface to which this address is associated.
local - is a local permanent fdb entry
static - is a static (no arp) fdb entry
dynamic - is a dynamic reachable age-able fdb entry
self - the address is associated with the port drivers fdb.
Usually hardware.
master - the address is associated with master devices fdb.
Usually software (default).
router - the destination address is associated with a router.
Valid if the referenced device is a VXLAN type device and has
route short circuit enabled.
use - the address is in use. User space can use this option to
indicate to the kernel that the fdb entry is in use.
extern_learn - this entry was learned externally. This option
can be used to indicate to the kernel that an entry was
hardware or user-space controller learnt dynamic entry. Kernel
will not age such an entry.
sticky - this entry will not change its port due to learning.
The next command line parameters apply only when the specified device
DEV is of type VXLAN.
dst IPADDR
the IP address of the destination VXLAN tunnel endpoint where
the Ethernet MAC ADDRESS resides.
src_vni VNI
the src VNI Network Identifier (or VXLAN Segment ID) this
entry belongs to. Used only when the vxlan device is in
external or collect metadata mode. If omitted the value
specified at vxlan device creation will be used.
vni VNI
the VXLAN VNI Network Identifier (or VXLAN Segment ID) to use
to connect to the remote VXLAN tunnel endpoint. If omitted
the value specified at vxlan device creation will be used.
port PORT
the UDP destination PORT number to use to connect to the
remote VXLAN tunnel endpoint. If omitted the default value is
used.
via DEVICE
device name of the outgoing interface for the VXLAN device
driver to reach the remote VXLAN tunnel endpoint.
bridge fdb append - append a forwarding database entry
This command adds a new fdb entry with an already known LLADDR.
Valid only for multicast link layer addresses. The command adds
support for broadcast and multicast Ethernet MAC addresses. The
Ethernet MAC address is added multiple times into the forwarding
database and the vxlan device driver sends a copy of the data packet
to each entry found.
The arguments are the same as with bridge fdb add.
bridge fdb delete - delete a forwarding database entry
This command removes an existing fdb entry.
The arguments are the same as with bridge fdb add.
bridge fdb replace - replace a forwarding database entry
If no matching entry is found, a new one will be created instead.
The arguments are the same as with bridge fdb add.
bridge fdb show - list forwarding entries.
This command displays the current forwarding table.
With the -statistics option, the command becomes verbose. It prints
out the last updated and last used time for each entry.
bridge fdb get - get bridge forwarding entry.
lookup a bridge forwarding table entry.
LLADDR the Ethernet MAC address.
dev DEV
the interface to which this address is associated.
brport DEV
the bridge port to which this address is associated. same as
dev above.
br DEV the bridge to which this address is associated.
self - the address is associated with the port drivers fdb. Usually
hardware.
master - the address is associated with master devices fdb. Usually
software (default).
mdb objects contain known IP multicast group addresses on a link.
The corresponding commands display mdb entries, add new entries, and
delete old ones.
bridge mdb add - add a new multicast group database entry
This command creates a new mdb entry.
dev DEV
the interface where this group address is associated.
port PORT
the port whose link is known to have members of this multicast
group.
grp GROUP
the IP multicast group address whose members reside on the
link connected to the port.
permanent - the mdb entry is permanent
temp - the mdb entry is temporary (default)
vid VID
the VLAN ID which is known to have members of this multicast
group.
bridge mdb delete - delete a multicast group database entry
This command removes an existing mdb entry.
The arguments are the same as with bridge mdb add.
bridge mdb show - list multicast group database entries
This command displays the current multicast group membership table.
The table is populated by IGMP and MLD snooping in the bridge driver
automatically. It can be altered by bridge mdb add and bridge mdb del
commands manually too.
dev DEV
the interface only whose entries should be listed. Default is
to list all bridge interfaces.
With the -details option, the command becomes verbose. It prints out
the ports known to have a connected router.
With the -statistics option, the command displays timer values for
mdb and router port entries.
vlan objects contain known VLAN IDs for a link.
The corresponding commands display vlan filter entries, add new
entries, and delete old ones.
bridge vlan add - add a new vlan filter entry
This command creates a new vlan filter entry.
dev NAME
the interface with which this vlan is associated.
vid VID
the VLAN ID that identifies the vlan.
tunnel_info TUNNEL_ID
the TUNNEL ID that maps to this vlan. The tunnel id is set in
dst_metadata for every packet that belongs to this vlan
(applicable to bridge ports with vlan_tunnel flag set).
pvid the vlan specified is to be considered a PVID at ingress. Any
untagged frames will be assigned to this VLAN.
untagged
the vlan specified is to be treated as untagged on egress.
self the vlan is configured on the specified physical device.
Required if the device is the bridge device.
master the vlan is configured on the software bridge (default).
bridge vlan delete - delete a vlan filter entry
This command removes an existing vlan filter entry.
The arguments are the same as with bridge vlan add. The pvid and
untagged flags are ignored.
bridge vlan show - list vlan configuration.
This command displays the current VLAN filter table.
With the -statistics option, the command displays per-vlan traffic
statistics.
bridge vlan tunnelshow - list vlan tunnel mapping.
This command displays the current vlan tunnel info mapping.
The bridge utility can monitor the state of devices and addresses
continuously. This option has a slightly different format. Namely,
the monitor command is the first in the command line and then the
object list follows:
bridge monitor [ all | OBJECT-LIST ]
OBJECT-LIST is the list of object types that we want to monitor. It
may contain link, fdb, and mdb. If no file argument is given, bridge
opens RTNETLINK, listens on it and dumps state changes in the format
described in previous sections.
If a file name is given, it does not listen on RTNETLINK, but opens
the file containing RTNETLINK messages saved in binary format and
dumps them.
This command uses facilities added in Linux 3.0.
Although the forwarding table is maintained on a per-bridge device
basis the bridge device is not part of the syntax. This is a
limitation of the underlying netlink neighbour message protocol. When
displaying the forwarding table, entries for all bridges are
displayed. Add/delete/modify commands determine the underlying
bridge device based on the bridge to which the corresponding ethernet
device is attached.
ip(8)
Please direct bugreports and patches to: <netdev@vger.kernel.org>
Original Manpage by Stephen Hemminger
This page is part of the iproute2 (utilities for controlling TCP/IP
networking and traffic) project. Information about the project can
be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
netdev@vger.kernel.org, shemminger@osdl.org. This page was obtained
from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2020-06-09. (At that time, the date of the most recent commit that
was found in the repository was 2020-06-05.) 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
iproute2 1 August 2012 BRIDGE(8)
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