bridge(8) — Linux manual page

NAME | SYNOPSIS | OPTIONS | BRIDGE - COMMAND SYNTAX | bridge link - bridge port | bridge fdb - forwarding database management | bridge mdb - multicast group database management | bridge vlan - VLAN filter list | bridge monitor - state monitoring | NOTES | SEE ALSO | BUGS | AUTHOR | COLOPHON

BRIDGE(8)                         Linux                        BRIDGE(8)

NAME         top

       bridge - show / manipulate bridge addresses and devices

SYNOPSIS         top

       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 set dev DEV vid VID [ state STP_STATE ]

       bridge vlan [ show | tunnelshow ] [ dev DEV ]

       bridge monitor [ all | neigh | link | mdb | vlan ]

OPTIONS         top

       -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         top

   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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       ip(8)

BUGS         top

       Please direct bugreports and patches to: <netdev@vger.kernel.org>

AUTHOR         top

       Original Manpage by Stephen Hemminger

COLOPHON         top

       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
       2021-06-20.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-06-17.)  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)