BRIDGE
Section: Linux (8)
Updated: 1 August 2012
Page Index
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 } ] [
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 ]
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.
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 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.
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. 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.
- 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 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)
- 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 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.
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, 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