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Secure Inter-Network Operations

bridge(8) - phpMan

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] }

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 } ] [ flood { on | off } ] [ hwmode { vepa | veb } ]

bridge link [ show ] [ dev DEV ]

bridge fdb { add | append | del } LLADDR dev DEV { local | temp } { self } { embedded } {
router } [ dst IPADDR ] [ vni VNI ] [ port PORT ] [ via DEVICE ]

bridge fdb [ show ] [ dev DEV ]

bridge mdb { add | del } dev DEV port PORT grp GROUP [ permanent | temp ]

bridge mdb show [ dev DEV ]

bridge vlan { add | del } dev DEV vid VID [ pvid ] [ untagged ] [ self ] [ master ]

bridge vlan [ show ] [ 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 val‐
ues.

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
selectio algorithms.

state STATE
the operation state of the port. This is primarily used by user space STP/RSTP
implementation. The following is a list of valid values:

0 - port is DISABLED. Make this port completely inactive.

1 - STP LISTENING state. Only valid if STP is enabled on the brige. In this state
the port for list for STP BPDUs and drop all other traffic.

2 - 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 adress tables.

3 - STP FORWARDING state. Port is fully active.

4 - 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 BPUDs will be processed by the bridge port. By default, the
flag is turned off allowed BPDU processing. Turning this flag on will cause the
port to stop processing STP BPDUs.

hairpin on or hairpin off
Controls whether traffic may be send back out of the port on which it was received.
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.

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.

flooding on or flooding 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 con‐
figured 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.

bridge link show - list bridge port configuration.
This command displays the current bridge port configuration and flags.

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.

self - the address is associated with a software fdb (default)

embedded - the address is associated with an offloaded fdb

router - the destination address is associated with a router. Valid if the refer‐
enced device is a VXLAN type device and has route shortcircuit enabled.

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.

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 cre‐
ation will be used.

port PORT
the UDP destination PORT number to use to connect to the remote VXLAN tunnel end‐
point. 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 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 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)

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.

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.

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 forwarding database entry
This command removes an existing fdb 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.

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. Such a history file can be gen‐
erated with the

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 mes‐
sage protocol. When displaying the forwarding table, entries for all bridges are dis‐
played. Add/delete/modify commands determine the underlying bridge device based on the
bridge to which the corresponding ethernet device is attached.