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 [ 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         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 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 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         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

              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         top

       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
       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 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         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, 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
       2020-09-18.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-09-14.)  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)