BRIDGE(8) Linux BRIDGE(8)
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[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 } ] [ hw-
mode { 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 ] [ ex-
tern_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 ]
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 MDB router ports.
-n, -net, -netns <NETNS>
switches bridge to the specified network namespace NETNS. Actu-
ally 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 ap-
plication 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 ac-
tions 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 com-
mands 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 spe-
cific 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 in-
sensitive), or one of the numbers below. Negative inputs are ig-
nored, and unrecognized names return an error.
0 - port is in STP DISABLED state. Make this port completely in-
active 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 net-
work 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 re-
lay 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 re-
ceiving port.
fastleave on or fastleave off
This flag allows the bridge to immediately stop multicast traf-
fic 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 re-
ceived 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 down-
stream 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 re-
ceived traffic or not. If learning if off, the bridge will end
up flooding any traffic for which it has no FDB entry. By de-
fault 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 ex-
ternal 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 uni-
cast 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 mul-
ticast router.
neigh_suppress on or neigh_suppress off
Controls whether neigh discovery (arp and nd) proxy and suppres-
sion 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
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. Usu-
ally hardware.
master - the address is associated with master devices fdb. Usu-
ally 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 ad-
dress 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 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 auto-
matically. It can be altered by bridge mdb add and bridge mdb del com-
mands 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 en-
tries, 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 (appli-
cable 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. Re-
quired 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 un-
tagged 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 sta-
tistics.
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 con-
tinuously. 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.
NOTES
This command uses facilities added in Linux 3.0.
Although the forwarding table is maintained on a per-bridge device ba-
sis 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)