Provided by: iproute2_5.15.0-1ubuntu2_amd64 
NAME
bridge - show / manipulate bridge addresses and devices
SYNOPSIS
bridge [ OPTIONS ] OBJECT { COMMAND | help }
OBJECT := { link | fdb | mdb | vlan | monitor }
OPTIONS := { -V[ersion] | -s[tatistics] | -n[etns] name | -b[atch] filename | -c[olor] | -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 set dev DEV vid VID [ state STP_STATE ]
bridge vlan [ show | tunnelshow ] [ dev DEV ]
bridge monitor [ all | neigh | link | mdb | vlan ]
OPTIONS
-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 bridge vlan filter entries or 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.
BRIDGE - COMMAND SYNTAX
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.
bridge link - bridge port
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.
bridge fdb - forwarding database management
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).
bridge mdb - multicast group database management
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.
bridge vlan - VLAN filter list
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 set - change vlan filter entry's options
This command changes vlan filter entry's options.
dev NAME
the interface with which this vlan is associated.
vid VID
the VLAN ID that identifies the vlan.
state STP_STATE
the operation state of the vlan. One may enter STP state name (case insensitive), or one of the
numbers below. Negative inputs are ignored, and unrecognized names return an error. Note that the
state is set only for the vlan of the specified device, e.g. if it is a bridge port then the state
will be set only for the vlan of the port.
0 - vlan is in STP DISABLED state. Make this vlan completely inactive for STP. This is also called
BPDU filter and could be used to disable STP on an untrusted vlan.
1 - vlan is in STP LISTENING state. Only valid if STP is enabled on the bridge. In this state the
vlan listens for STP BPDUs and drops all other traffic frames.
2 - vlan is in STP LEARNING state. Only valid if STP is enabled on the bridge. In this state the
vlan will accept traffic only for the purpose of updating MAC address tables.
3 - vlan is in STP FORWARDING state. This is the default vlan state.
4 - vlan 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, the vlan will only process STP BPDUs.
bridge vlan show - list vlan configuration.
This command displays the current VLAN filter table.
With the -details option, the command becomes verbose. It displays the per-vlan options.
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.
bridge monitor - state monitoring
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, vlan 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.
NOTES
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.
SEE ALSO
ip(8)
BUGS
Please direct bugreports and patches to: <netdev@vger.kernel.org>
AUTHOR
Original Manpage by Stephen Hemminger
iproute2 1 August 2012 BRIDGE(8)