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 ] [ src_vni VNI ] { [
dst IPADDR ] [ vni VNI ] [ port PORT ] [ via DEVICE ] |
nhid NHID }
bridge fdb [ [ show ] [ br BRDEV ] [ brport DEV ] [ vlan VID ] [
state STATE ] [ dynamic ] ]
bridge fdb get [ to ] LLADDR [ br BRDEV ] { brport | dev } DEV [
vlan VID ] [ vni VNI ] [ self ] [ master ] [ dynamic ]
bridge mdb { add | del } dev DEV port PORT grp GROUP [ src SOURCE
] [ 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 unicast traffic for which there is no FDB
entry will be flooded towards this given port. 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 multicast traffic for which there is no
MDB entry will be flooded towards this given port. 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, which means that
the bridge will not forward frames with this destination
MAC address and VLAN ID, but terminate them locally. This
flag is default unless "static" or "dynamic" are
explicitly specified.
permanent - this is a synonym for "local"
static - is a static (no arp) fdb entry
dynamic - is a dynamic reachable age-able fdb entry
self - the operation is fulfilled directly by the driver
for the specified network device. If the network device
belongs to a master like a bridge, then the bridge is
bypassed and not notified of this operation (and if the
device does notify the bridge, it is driver-specific
behavior and not mandated by this flag, check the driver
for more details). The "bridge fdb add" command can also
be used on the bridge device itself, and in this case, the
added fdb entries will be locally terminated (not
forwarded). In the latter case, the "self" flag is
mandatory. The flag is set by default if "master" is not
specified.
master - if the specified network device is a port that
belongs to a master device such as a bridge, the operation
is fulfilled by the master device's driver, which may in
turn notify the port driver too of the address. If the
specified device is a master itself, such as a bridge,
this flag is invalid.
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.
nhid NHID
ecmp nexthop group for the VXLAN device driver to reach
remote VXLAN tunnel endpoints.
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 or L2 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 multicast group address (IPv4, IPv6 or L2 multicast)
whose members reside on the link connected to the port.
permanent - the mdb entry is permanent. Optional for IPv4
and IPv6, mandatory for L2.
temp - the mdb entry is temporary (default)
src SOURCE
optional source IP address of a sender for this multicast
group. If IGMPv3 for IPv4, or MLDv2 for IPv6 respectively,
are enabled it will be included in the lookup when
forwarding multicast traffic.
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
2021-04-01. (At that time, the date of the most recent commit
that was found in the repository was 2021-03-22.) 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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