Provided by: ebtables_2.0.10.4-3.4ubuntu1_amd64 bug

NAME

       ebtables - Ethernet bridge frame table administration

SYNOPSIS

       ebtables  [-t  table  ]  -[ACDI]  chain  rule  specification  [match  extensions] [watcher
       extensions] target
       ebtables [-t table ] -P chain ACCEPT | DROP | RETURN
       ebtables [-t table ] -F [chain]
       ebtables [-t table ] -Z [chain]
       ebtables [-t table ] -L [-Z] [chain] [ [--Ln] | [--Lx] ] [--Lc] [--Lmac2]
       ebtables [-t table ] -N chain [-P ACCEPT | DROP | RETURN]
       ebtables [-t table ] -X [chain]
       ebtables [-t table ] -E old-chain-name new-chain-name
       ebtables [-t table ] --init-table
       ebtables [-t table ] [--atomic-file file] --atomic-commit
       ebtables [-t table ] [--atomic-file file] --atomic-init
       ebtables [-t table ] [--atomic-file file] --atomic-save

DESCRIPTION

       ebtables is an application program used to set up and maintain the tables of rules (inside
       the  Linux  kernel)  that  inspect  Ethernet  frames.   It  is  analogous  to the iptables
       application, but less complicated, due to the fact that  the  Ethernet  protocol  is  much
       simpler than the IP protocol.

   CHAINS
       There are three ebtables tables with built-in chains in the Linux kernel. These tables are
       used to divide functionality into different sets of rules. Each set of rules is  called  a
       chain.   Each  chain is an ordered list of rules that can match Ethernet frames. If a rule
       matches an Ethernet frame, then a processing specification tells  what  to  do  with  that
       matching  frame.  The processing specification is called a 'target'. However, if the frame
       does not match the current rule in the chain, then the next rule in the chain is  examined
       and  so  forth.   The  user  can  create new (user-defined) chains that can be used as the
       'target' of a rule. User-defined chains are very useful to get better performance over the
       linear  traversal  of the rules and are also essential for structuring the filtering rules
       into well-organized and maintainable sets of rules.

   TARGETS
       A firewall  rule  specifies  criteria  for  an  Ethernet  frame  and  a  frame  processing
       specification  called  a  target.   When  a  frame  matches  a  rule, then the next action
       performed by the kernel is specified by the target.   The  target  can  be  one  of  these
       values:  ACCEPT,  DROP,  CONTINUE, RETURN, an 'extension' (see below) or a jump to a user-
       defined chain.

       ACCEPT means to let the frame through.  DROP means the frame has to  be  dropped.  In  the
       BROUTING  chain  however, the ACCEPT and DROP target have different meanings (see the info
       provided for the -t option).  CONTINUE means the next rule has to be checked. This can  be
       handy,  f.e.,  to  know  how  many  frames pass a certain point in the chain, to log those
       frames or to apply multiple targets on a frame.  RETURN means stop traversing  this  chain
       and  resume  at  the next rule in the previous (calling) chain.  For the extension targets
       please refer to the TARGET EXTENSIONS section of this man page.

   TABLES
       As stated earlier, there are three ebtables tables in the Linux kernel.  The  table  names
       are  filter, nat and broute.  Of these three tables, the filter table is the default table
       that the command operates on.  If you are working with the filter table, then you can drop
       the  '-t  filter' argument to the ebtables command.  However, you will need to provide the
       -t argument for the other two tables.   Moreover,  the  -t  argument  must  be  the  first
       argument on the ebtables command line, if used.

       -t, --table
              filter  is  the default table and contains three built-in chains: INPUT (for frames
              destined for the bridge itself, on the  level  of  the  MAC  destination  address),
              OUTPUT  (for  locally-generated  or (b)routed frames) and FORWARD (for frames being
              forwarded by the bridge).
              nat is mostly used to change the mac addresses and contains three built-in  chains:
              PREROUTING  (for  altering  frames  as  soon as they come in), OUTPUT (for altering
              locally generated or (b)routed frames before they are bridged) and POSTROUTING (for
              altering  frames as they are about to go out). A small note on the naming of chains
              PREROUTING and POSTROUTING: it would be more accurate to  call  them  PREFORWARDING
              and  POSTFORWARDING, but for all those who come from the iptables world to ebtables
              it is easier to have the same names. Note that you can change the name (-E) if  you
              don't like the default.
              broute is used to make a brouter, it has one built-in chain: BROUTING.  The targets
              DROP and ACCEPT have a special meaning in the broute table (these  names  are  used
              instead  of  more  descriptive  names  to  keep  the implementation generic).  DROP
              actually means the frame has to be routed, while ACCEPT means the frame has  to  be
              bridged.  The BROUTING chain is traversed very early. However, it is only traversed
              by frames entering on a bridge port that is in  forwarding  state.  Normally  those
              frames  would be bridged, but you can decide otherwise here. The redirect target is
              very handy here.

EBTABLES COMMAND LINE ARGUMENTS

       After the initial ebtables '-t table' command line argument, the remaining  arguments  can
       be  divided  into several groups.  These groups are commands, miscellaneous commands, rule
       specifications, match extensions, watcher extensions and target extensions.

   COMMANDS
       The ebtables command arguments specify the actions to perform on the  table  defined  with
       the -t argument.  If you do not use the -t argument to name a table, the commands apply to
       the default filter table.  Only one command may be used on the command  line  at  a  time,
       except  when  the commands -L and -Z are combined, the commands -N and -P are combined, or
       when --atomic-file is used.

       -A, --append
              Append a rule to the end of the selected chain.

       -D, --delete
              Delete the specified rule or rules from the selected chain. There are two  ways  to
              use  this command. The first is by specifying an interval of rule numbers to delete
              (directly after -D).  Syntax: start_nr[:end_nr] (use -L --Ln to list the rules with
              their  rule  number).  When end_nr is omitted, all rules starting from start_nr are
              deleted. Using negative numbers is allowed, for more details about  using  negative
              numbers, see the -I command. The second usage is by specifying the complete rule as
              it would have been specified when it was added. Only  the  first  encountered  rule
              that  is the same as this specified rule, in other words the matching rule with the
              lowest (positive) rule number, is deleted.

       -C, --change-counters
              Change the counters of the specified rule or rules from the selected  chain.  There
              are  two  ways  to use this command. The first is by specifying an interval of rule
              numbers to do the changes on (directly after -C).  Syntax:  start_nr[:end_nr]  (use
              -L  --Ln to list the rules with their rule number). The details are the same as for
              the -D command. The second usage is by specifying the complete  rule  as  it  would
              have  been  specified when it was added. Only the counters of the first encountered
              rule that is the same as this specified rule, in other words the matching rule with
              the  lowest  (positive) rule number, are changed.  In the first usage, the counters
              are specified directly after  the  interval  specification,  in  the  second  usage
              directly  after  -C.  First the packet counter is specified, then the byte counter.
              If the specified counters start with a '+', the counter values  are  added  to  the
              respective current counter values.  If the specified counters start with a '-', the
              counter values are decreased from the respective current counter values. No  bounds
              checking is done. If the counters don't start with '+' or '-', the current counters
              are changed to the specified counters.

       -I, --insert
              Insert the specified rule into the selected chain at the specified rule number.  If
              the  rule  number is not specified, the rule is added at the head of the chain.  If
              the current number of rules equals N, then the specified number can be  between  -N
              and N+1.  For a positive number i, it holds that i and i-N-1 specify the same place
              in the chain where the rule should be inserted. The rule  number  0  specifies  the
              place past the last rule in the chain and using this number is therefore equivalent
              to using the -A command.  Rule numbers structly smaller than 0 can be  useful  when
              more than one rule needs to be inserted in a chain.

       -P, --policy
              Set the policy for the chain to the given target. The policy can be ACCEPT, DROP or
              RETURN.

       -F, --flush
              Flush the selected chain. If no  chain  is  selected,  then  every  chain  will  be
              flushed. Flushing a chain does not change the policy of the chain, however.

       -Z, --zero
              Set  the  counters  of the selected chain to zero. If no chain is selected, all the
              counters are set to zero. The -Z command can be used in  conjunction  with  the  -L
              command.   When both the -Z and -L commands are used together in this way, the rule
              counters are printed on the screen before they are set to zero.

       -L, --list
              List all rules in the selected chain. If no  chain  is  selected,  all  chains  are
              listed.
              The following options change the output of the -L command.
              --Ln
              Places the rule number in front of every rule. This option is incompatible with the
              --Lx option.
              --Lc
              Shows the counters at the end of each rule displayed by  the  -L  command.  Both  a
              frame  counter  (pcnt)  and a byte counter (bcnt) are displayed.  The frame counter
              shows how many frames have matched the specific rule, the byte  counter  shows  the
              sum  of  the frame sizes of these matching frames. Using this option in combination
              with the --Lx option causes the counters to  be  written  out  in  the  '-c  <pcnt>
              <bcnt>' option format.
              --Lx
              Changes  the  output  so that it produces a set of ebtables commands that construct
              the contents of the chain, when specified.  If  no  chain  is  specified,  ebtables
              commands  to  construct the contents of the table are given, including commands for
              creating the user-defined chains (if any).  You can use this set of commands in  an
              ebtables  boot  or  reload  script.  For example the output could be used at system
              startup.  The --Lx option is incompatible with the --Ln listing option.  Using  the
              --Lx option together with the --Lc option will cause the counters to be written out
              in the '-c <pcnt> <bcnt>' option format.
              --Lmac2
              Shows all MAC addresses with the same length, adding leading zeroes  if  necessary.
              The default representation omits leading zeroes in the addresses.

       -N, --new-chain
              Create  a  new  user-defined  chain with the given name. The number of user-defined
              chains is limited only by the number of possible chain names.  A user-defined chain
              name has a maximum length of 31 characters. The standard policy of the user-defined
              chain is ACCEPT. The policy of the new chain can  be  initialized  to  a  different
              standard target by using the -P command together with the -N command. In this case,
              the chain name does not have to be specified for the -P command.

       -X, --delete-chain
              Delete the specified user-defined chain. There  must  be  no  remaining  references
              (jumps)  to the specified chain, otherwise ebtables will refuse to delete it. If no
              chain is specified, all user-defined chains that aren't referenced will be removed.

       -E, --rename-chain
              Rename the specified chain to a new name.  Besides renaming a  user-defined  chain,
              you  can  rename  a standard chain to a name that suits your taste. For example, if
              you like PREFORWARDING more than PREROUTING, then you can use  the  -E  command  to
              rename  the  PREROUTING  chain. If you do rename one of the standard ebtables chain
              names, please be sure to mention this fact  should  you  post  a  question  on  the
              ebtables  mailing  lists.   It would be wise to use the standard name in your post.
              Renaming a standard ebtables chain in this fashion has no effect on  the  structure
              or functioning of the ebtables kernel table.

       --init-table
              Replace the current table data by the initial table data.

       --atomic-init
              Copy the kernel's initial data of the table to the specified file. This can be used
              as the first action, after which rules are added to  the  file.  The  file  can  be
              specified  using  the  --atomic-file  command  or  through the EBTABLES_ATOMIC_FILE
              environment variable.

       --atomic-save
              Copy the kernel's current data of the table to the specified file. This can be used
              as  the  first  action,  after  which  rules are added to the file. The file can be
              specified using the  --atomic-file  command  or  through  the  EBTABLES_ATOMIC_FILE
              environment variable.

       --atomic-commit
              Replace  the  kernel table data with the data contained in the specified file. This
              is a useful command that allows you to load all your rules of a certain table  into
              the  kernel  at  once, saving the kernel a lot of precious time and allowing atomic
              updates of the tables. The file which contains the table  data  is  constructed  by
              using  either the --atomic-init or the --atomic-save command to generate a starting
              file. After that, using  the  --atomic-file  command  when  constructing  rules  or
              setting the EBTABLES_ATOMIC_FILE environment variable allows you to extend the file
              and build the complete table before committing it to the kernel. This  command  can
              be very useful in boot scripts to populate the ebtables tables in a fast way.

   MISCELLANOUS COMMANDS
       -V, --version
              Show the version of the ebtables userspace program.

       -h, --help [list of module names]
              Give  a brief description of the command syntax. Here you can also specify names of
              extensions and ebtables will  try  to  write  help  about  those  extensions.  E.g.
              ebtables  -h  snat  log  ip  arp.   Specify  list_extensions to list all extensions
              supported by the userspace utility.

       -j, --jump target
              The target of the rule.  This  is  one  of  the  following  values:  ACCEPT,  DROP,
              CONTINUE,  RETURN,  a  target  extension  (see TARGET EXTENSIONS) or a user-defined
              chain name.

       --atomic-file file
              Let the command operate on the specified file.  The data of the table to operate on
              will  be extracted from the file and the result of the operation will be saved back
              into  the  file.  If  specified,  this  option  should  come  before  the   command
              specification.   An   alternative   that   should  be  preferred,  is  setting  the
              EBTABLES_ATOMIC_FILE environment variable.

       -M, --modprobe program
              When talking to the kernel, use this program to try to automatically  load  missing
              kernel modules.

       --concurrent
              Use a file lock to support concurrent scripts updating the ebtables kernel tables.

   RULE SPECIFICATIONS
       The  following command line arguments make up a rule specification (as used in the add and
       delete commands). A "!"  option  before  the  specification  inverts  the  test  for  that
       specification.  Apart from these standard rule specifications there are some other command
       line arguments of interest.  See both the MATCH  EXTENSIONS  and  the  WATCHER  EXTENSIONS
       below.

       -p, --protocol [!] protocol
              The protocol that was responsible for creating the frame. This can be a hexadecimal
              number, above 0x0600, a name (e.g.  ARP ) or LENGTH.  The  protocol  field  of  the
              Ethernet  frame  can  be  used  to  denote  the  length  of the header (802.2/802.3
              networks). When the value of that field is below or equals 0x0600, the value equals
              the  size  of  the  header and shouldn't be used as a protocol number. Instead, all
              frames where the protocol field is used as the length field are assumed  to  be  of
              the same 'protocol'. The protocol name used in ebtables for these frames is LENGTH.
              The  file  /etc/ethertypes  can  be  used  to  show  readable characters instead of
              hexadecimal numbers for the protocols. For example, 0x0800 will be  represented  by
              IPV4.   The  use  of  this  file  is  not  case  sensitive.  See that file for more
              information. The flag --proto is an alias for this option.

       -i, --in-interface [!] name
              The interface (bridge port) via which a frame is received (this option is useful in
              the  INPUT,  FORWARD,  PREROUTING  and BROUTING chains). If the interface name ends
              with '+', then any interface name that begins with  this  name  (disregarding  '+')
              will match.  The flag --in-if is an alias for this option.

       --logical-in [!] name
              The (logical) bridge interface via which a frame is received (this option is useful
              in the INPUT, FORWARD, PREROUTING and BROUTING chains).  If the interface name ends
              with  '+',  then  any  interface name that begins with this name (disregarding '+')
              will match.

       -o, --out-interface [!] name
              The interface (bridge port) via which a frame is going to be sent (this  option  is
              useful  in  the OUTPUT, FORWARD and POSTROUTING chains). If the interface name ends
              with '+', then any interface name that begins with  this  name  (disregarding  '+')
              will match.  The flag --out-if is an alias for this option.

       --logical-out [!] name
              The  (logical)  bridge interface via which a frame is going to be sent (this option
              is useful in the OUTPUT, FORWARD and POSTROUTING chains).  If  the  interface  name
              ends  with  '+',  then  any interface name that begins with this name (disregarding
              '+') will match.

       -s, --source [!] address[/mask]
              The source MAC address. Both mask and address are written as 6 hexadecimal  numbers
              separated by colons. Alternatively one can specify Unicast, Multicast, Broadcast or
              BGA (Bridge Group Address):
              Unicast=00:00:00:00:00:00/01:00:00:00:00:00,
              Multicast=01:00:00:00:00:00/01:00:00:00:00:00,
              Broadcast=ff:ff:ff:ff:ff:ff/ff:ff:ff:ff:ff:ff                                    or
              BGA=01:80:c2:00:00:00/ff:ff:ff:ff:ff:ff.   Note  that a broadcast address will also
              match the multicast specification. The flag --src is an alias for this option.

       -d, --destination [!] address[/mask]
              The destination MAC address. See -s (above) for more details on MAC addresses.  The
              flag --dst is an alias for this option.

       -c, --set-counter pcnt bcnt
              If  used  with  -A or -I, then the packet and byte counters of the new rule will be
              set to pcnt, resp. bcnt.  If used with the -C or -D commands,  only  rules  with  a
              packet and byte count equal to pcnt, resp. bcnt will match.

   MATCH EXTENSIONS
       Ebtables  extensions are dynamically loaded into the userspace tool, there is therefore no
       need to explicitly load them with a -m option like is done in iptables.  These  extensions
       deal  with  functionality  supported  by  kernel modules supplemental to the core ebtables
       code.

   802_3
       Specify 802.3 DSAP/SSAP fields or SNAP type.  The protocol must  be  specified  as  LENGTH
       (see the option  -p above).

       --802_3-sap [!] sap
              DSAP  and  SSAP are two one byte 802.3 fields.  The bytes are always equal, so only
              one byte (hexadecimal) is needed as an argument.

       --802_3-type [!] type
              If the 802.3 DSAP and SSAP values are  0xaa  then  the  SNAP  type  field  must  be
              consulted  to  determine  the  payload  protocol.  This is a two byte (hexadecimal)
              argument.  Only 802.3 frames with DSAP/SSAP 0xaa are checked for type.

   among
       Match a MAC address or MAC/IP address pair versus a  list  of  MAC  addresses  and  MAC/IP
       address pairs.  A list entry has the following format: xx:xx:xx:xx:xx:xx[=ip.ip.ip.ip][,].
       Multiple list entries are separated by a comma, specifying an IP address corresponding  to
       the  MAC  address is optional. Multiple MAC/IP address pairs with the same MAC address but
       different IP address (and vice versa) can be specified. If the MAC address  doesn't  match
       any entry from the list, the frame doesn't match the rule (unless "!" was used).

       --among-dst [!] list
              Compare  the MAC destination to the given list. If the Ethernet frame has type IPv4
              or ARP, then comparison with MAC/IP destination address  pairs  from  the  list  is
              possible.

       --among-src [!] list
              Compare  the  MAC  source to the given list. If the Ethernet frame has type IPv4 or
              ARP, then comparison with MAC/IP source address pairs from the list is possible.

       --among-dst-file [!] file
              Same as --among-dst but the list is read in from the specified file.

       --among-src-file [!] file
              Same as --among-src but the list is read in from the specified file.

   arp
       Specify (R)ARP fields. The protocol must be specified as ARP or RARP.

       --arp-opcode [!] opcode
              The (R)ARP opcode (decimal or a string, for more details see ebtables -h arp).

       --arp-htype [!] hardware type
              The hardware type, this can be a decimal or the string Ethernet (which sets type to
              1). Most (R)ARP packets have Eternet as hardware type.

       --arp-ptype [!] protocol type
              The  protocol  type  for  which the (r)arp is used (hexadecimal or the string IPv4,
              denoting 0x0800).  Most (R)ARP packets have protocol type IPv4.

       --arp-ip-src [!] address[/mask]
              The (R)ARP IP source address specification.

       --arp-ip-dst [!] address[/mask]
              The (R)ARP IP destination address specification.

       --arp-mac-src [!] address[/mask]
              The (R)ARP MAC source address specification.

       --arp-mac-dst [!] address[/mask]
              The (R)ARP MAC destination address specification.

       [!] --arp-gratuitous
              Checks for ARP gratuitous packets: checks equality of IPv4 source address and  IPv4
              destination address inside the ARP header.

   ip
       Specify IPv4 fields. The protocol must be specified as IPv4.

       --ip-source [!] address[/mask]
              The source IP address.  The flag --ip-src is an alias for this option.

       --ip-destination [!] address[/mask]
              The destination IP address.  The flag --ip-dst is an alias for this option.

       --ip-tos [!] tos
              The IP type of service, in hexadecimal numbers.  IPv4.

       --ip-protocol [!] protocol
              The IP protocol.  The flag --ip-proto is an alias for this option.

       --ip-source-port [!] port1[:port2]
              The  source port or port range for the IP protocols 6 (TCP), 17 (UDP), 33 (DCCP) or
              132 (SCTP). The --ip-protocol option must be specified as TCP, UDP, DCCP  or  SCTP.
              If port1 is omitted, 0:port2 is used; if port2 is omitted but a colon is specified,
              port1:65535 is used.  The flag --ip-sport is an alias for this option.

       --ip-destination-port [!] port1[:port2]
              The destination port or port range for ip protocols 6 (TCP), 17 (UDP), 33 (DCCP) or
              132  (SCTP).  The --ip-protocol option must be specified as TCP, UDP, DCCP or SCTP.
              If port1 is omitted, 0:port2 is used; if port2 is omitted but a colon is specified,
              port1:65535 is used.  The flag --ip-dport is an alias for this option.

   ip6
       Specify IPv6 fields. The protocol must be specified as IPv6.

       --ip6-source [!] address[/mask]
              The source IPv6 address.  The flag --ip6-src is an alias for this option.

       --ip6-destination [!] address[/mask]
              The destination IPv6 address.  The flag --ip6-dst is an alias for this option.

       --ip6-tclass [!] tclass
              The IPv6 traffic class, in hexadecimal numbers.

       --ip6-protocol [!] protocol
              The IP protocol.  The flag --ip6-proto is an alias for this option.

       --ip6-source-port [!] port1[:port2]
              The  source  port or port range for the IPv6 protocols 6 (TCP), 17 (UDP), 33 (DCCP)
              or 132 (SCTP). The --ip6-protocol option must be specified as  TCP,  UDP,  DCCP  or
              SCTP.   If  port1  is  omitted, 0:port2 is used; if port2 is omitted but a colon is
              specified, port1:65535 is used.  The flag --ip6-sport is an alias for this option.

       --ip6-destination-port [!] port1[:port2]
              The destination port or port range for IPv6 protocols 6 (TCP), 17 (UDP), 33  (DCCP)
              or  132  (SCTP).  The  --ip6-protocol option must be specified as TCP, UDP, DCCP or
              SCTP.  If port1 is omitted, 0:port2 is used; if port2 is omitted  but  a  colon  is
              specified, port1:65535 is used.  The flag --ip6-dport is an alias for this option.

       --ip6-icmp-type [!] {type[:type]/code[:code]|typename}
              Specify  ipv6-icmp  type  and  code  to  match.   Ranges for both type and code are
              supported. Type and code are separated by a slash. Valid numbers for type and range
              are 0 to 255.  To match a single type including all valid codes, symbolic names can
              be used instead of numbers. The list of known type names is shown by the command
                ebtables --help ip6
              This option is only valid for --ip6-prococol ipv6-icmp.

   limit
       This module matches at a limited rate using a token bucket  filter.   A  rule  using  this
       extension  will  match until this limit is reached.  It can be used with the --log watcher
       to give limited logging, for example. Its use is the same as the limit match of iptables.

       --limit [value]
              Maximum average matching rate: specified as a number,  with  an  optional  /second,
              /minute, /hour, or /day suffix; the default is 3/hour.

       --limit-burst [number]
              Maximum initial number of packets to match: this number gets recharged by one every
              time the limit specified above is not reached, up to this number; the default is 5.

   mark_m
       --mark [!] [value][/mask]
              Matches frames with the given  unsigned  mark  value.  If  a  value  and  mask  are
              specified,  the  logical  AND of the mark value of the frame and the user-specified
              mask is taken before comparing it with the user-specified mark value. When  only  a
              mark  value  is specified, the packet only matches when the mark value of the frame
              equals the user-specified mark value.  If only a mask is specified, the logical AND
              of  the  mark value of the frame and the user-specified mask is taken and the frame
              matches when the result of this logical AND is non-zero. Only specifying a mask  is
              useful to match multiple mark values.

   pkttype
       --pkttype-type [!] type
              Matches  on  the  Ethernet "class" of the frame, which is determined by the generic
              networking code. Possible values:  broadcast  (MAC  destination  is  the  broadcast
              address), multicast (MAC destination is a multicast address), host (MAC destination
              is the receiving network device), or otherhost (none of the above).

   stp
       Specify stp BPDU (bridge protocol data unit) fields. The destination address (-d) must  be
       specified  as the bridge group address (BGA).  For all options for which a range of values
       can be specified, it holds that if the lower bound is omitted (but the colon is not), then
       the  lowest  possible  lower  bound  for  that option is used, while if the upper bound is
       omitted (but the colon again is not), the highest possible upper bound for that option  is
       used.

       --stp-type [!] type
              The  BPDU  type  (0-255),  recognized  non-numerical  types  are config, denoting a
              configuration BPDU (=0), and tcn, denothing a  topology  change  notification  BPDU
              (=128).

       --stp-flags [!] flag
              The BPDU flag (0-255), recognized non-numerical flags are topology-change, denoting
              the topology change flag  (=1),  and  topology-change-ack,  denoting  the  topology
              change acknowledgement flag (=128).

       --stp-root-prio [!] [prio][:prio]
              The root priority (0-65535) range.

       --stp-root-addr [!] [address][/mask]
              The root mac address, see the option -s for more details.

       --stp-root-cost [!] [cost][:cost]
              The root path cost (0-4294967295) range.

       --stp-sender-prio [!] [prio][:prio]
              The BPDU's sender priority (0-65535) range.

       --stp-sender-addr [!] [address][/mask]
              The BPDU's sender mac address, see the option -s for more details.

       --stp-port [!] [port][:port]
              The port identifier (0-65535) range.

       --stp-msg-age [!] [age][:age]
              The message age timer (0-65535) range.

       --stp-max-age [!] [age][:age]
              The max age timer (0-65535) range.

       --stp-hello-time [!] [time][:time]
              The hello time timer (0-65535) range.

       --stp-forward-delay [!] [delay][:delay]
              The forward delay timer (0-65535) range.

   vlan
       Specify  802.1Q  Tag Control Information fields.  The protocol must be specified as 802_1Q
       (0x8100).

       --vlan-id [!] id
              The VLAN identifier field (VID). Decimal number from 0 to 4095.

       --vlan-prio [!] prio
              The user priority field, a decimal number from 0 to 7.  The VID should be set to  0
              ("null VID") or unspecified (in the latter case the VID is deliberately set to 0).

       --vlan-encap [!] type
              The  encapsulated  Ethernet  frame  type/length.  Specified as a hexadecimal number
              from 0x0000 to 0xFFFF or as a symbolic name from /etc/ethertypes.

   WATCHER EXTENSIONS
       Watchers only look at frames passing by, they don't modify them nor decide to  accept  the
       frames  or  not. These watchers only see the frame if the frame matches the rule, and they
       see it before the target is executed.

   log
       The log watcher writes descriptive data about a frame to the syslog.

       --log
              Log with the default loggin options: log-level= info, log-prefix="", no ip logging,
              no arp logging.

       --log-level level
              Defines  the  logging  level.  For  the  possible values, see ebtables -h log.  The
              default level is info.

       --log-prefix text
              Defines the prefix text to be printed at the beginning of the line with the logging
              information.

       --log-ip
              Will  log the ip information when a frame made by the ip protocol matches the rule.
              The default is no ip information logging.

       --log-ip6
              Will log the ipv6 information when a frame made by the ipv6  protocol  matches  the
              rule. The default is no ipv6 information logging.

       --log-arp
              Will  log  the (r)arp information when a frame made by the (r)arp protocols matches
              the rule. The default is no (r)arp information logging.

   nflog
       The nflog watcher passes the packet to the loaded logging backend  in  order  to  log  the
       packet.  This  is usually used in combination with nfnetlink_log as logging backend, which
       will multicast the packet through a netlink socket to the specified multicast  group.  One
       or more userspace processes may subscribe to the group to receive the packets.

       --nflog
              Log with the default logging options

       --nflog-group nlgroup
              The  netlink  group  (1  -  2^32-1)  to  which  packets  are  (only  applicable for
              nfnetlink_log). The default value is 1.

       --nflog-prefix prefix
              A prefix string to include in the log message, up to 30 characters long, useful for
              distinguishing messages in the logs.

       --nflog-range size
              The  number of bytes to be copied to userspace (only applicable for nfnetlink_log).
              nfnetlink_log instances may specify their own range, this option overrides it.

       --nflog-threshold size
              Number of packets to queue inside the kernel before sending them to userspace (only
              applicable  for  nfnetlink_log).  Higher values result in less overhead per packet,
              but increase delay until the packets reach userspace. The default value is 1.

   ulog
       The ulog watcher passes the packet to a userspace logging daemon using  netlink  multicast
       sockets.  This  differs from the log watcher in the sense that the complete packet is sent
       to userspace instead of a descriptive text and that netlink  multicast  sockets  are  used
       instead  of  the syslog.  This watcher enables parsing of packets with userspace programs,
       the physical bridge in and out ports are also included in the netlink messages.  The  ulog
       watcher  module  accepts 2 parameters when the module is loaded into the kernel (e.g. with
       modprobe): nlbufsiz specifies how big the buffer for each netlink multicast group  is.  If
       you  say nlbufsiz=8192, for example, up to eight kB of packets will get accumulated in the
       kernel until they are sent to userspace. It is not possible to allocate more  than  128kB.
       Please  also  keep  in  mind  that  this buffer size is allocated for each nlgroup you are
       using, so the total kernel memory usage increases by that factor.  The  default  is  4096.
       flushtimeout  specifies after how many hundredths of a second the queue should be flushed,
       even if it is not full yet. The default is 10 (one tenth of a second).

       --ulog
              Use the default settings: ulog-prefix="", ulog-nlgroup=1, ulog-cprange=4096,  ulog-
              qthreshold=1.

       --ulog-prefix text
              Defines the prefix included with the packets sent to userspace.

       --ulog-nlgroup group
              Defines  which  netlink group number to use (a number from 1 to 32).  Make sure the
              netlink group numbers used for the iptables ULOG target differ from those used  for
              the ebtables ulog watcher.  The default group number is 1.

       --ulog-cprange range
              Defines  the  maximum  copy  range to userspace, for packets matching the rule. The
              default range is 0, which means the maximum copy range is  given  by  nlbufsiz.   A
              maximum  copy  range  larger  than  128*1024  is meaningless as the packets sent to
              userspace have an upper size limit of 128*1024.

       --ulog-qthreshold threshold
              Queue at most threshold number of packets before sending them to userspace  with  a
              netlink  socket.  Note  that  packets  can be sent to userspace before the queue is
              full, this happens when the ulog kernel timer goes off (the frequency of this timer
              depends on flushtimeout).

   TARGET EXTENSIONS
   arpreply
       The  arpreply target can be used in the PREROUTING chain of the nat table.  If this target
       sees an ARP request it will automatically reply with an ARP reply. The  used  MAC  address
       for  the  reply  can  be  specified.  The protocol must be specified as ARP.  When the ARP
       message is not an ARP request or when the ARP request  isn't  for  an  IP  address  on  an
       Ethernet  network,  it  is  ignored  by  this  target (CONTINUE).  When the ARP request is
       malformed, it is dropped (DROP).

       --arpreply-mac address
              Specifies the MAC address to reply with:  the  Ethernet  source  MAC  and  the  ARP
              payload source MAC will be filled in with this address.

       --arpreply-target target
              Specifies  the  standard target. After sending the ARP reply, the rule still has to
              give a standard target so ebtables knows what to do  with  the  ARP  request.   The
              default target is DROP.

   dnat
       The  dnat  target  can  only  be  used  in  the BROUTING chain of the broute table and the
       PREROUTING and OUTPUT chains of the nat table.  It  specifies  that  the  destination  MAC
       address has to be changed.

       --to-destination address
              Change  the destination MAC address to the specified address.  The flag --to-dst is
              an alias for this option.

       --dnat-target target
              Specifies the standard target. After doing the dnat, the rule still has to  give  a
              standard  target  so  ebtables knows what to do with the dnated frame.  The default
              target is ACCEPT.  Making it CONTINUE could let you use multiple target  extensions
              on  the same frame. Making it DROP only makes sense in the BROUTING chain but using
              the redirect target is more logical there. RETURN is also allowed. Note that  using
              RETURN in a base chain is not allowed (for obvious reasons).

   mark
       The  mark  target  can  be  used  in every chain of every table. It is possible to use the
       marking of a frame/packet in both ebtables and iptables, if the bridge-nf code is compiled
       into  the  kernel.  Both  put  the  marking  at  the same place. This allows for a form of
       communication between ebtables and iptables.

       --mark-set value
              Mark the frame with the specified non-negative value.

       --mark-or value
              Or the frame with the specified non-negative value.

       --mark-and value
              And the frame with the specified non-negative value.

       --mark-xor value
              Xor the frame with the specified non-negative value.

       --mark-target target
              Specifies the standard target. After marking the frame, the rule still has to  give
              a  standard  target  so  ebtables  knows what to do.  The default target is ACCEPT.
              Making it CONTINUE can let you do other things with the frame in  subsequent  rules
              of the chain.

   redirect
       The  redirect  target  will change the MAC target address to that of the bridge device the
       frame arrived on. This target can only be used in the BROUTING chain of the  broute  table
       and  the PREROUTING chain of the nat table.  In the BROUTING chain, the MAC address of the
       bridge port is used as destination address, in the PREROUTING chain, the  MAC  address  of
       the bridge is used.

       --redirect-target target
              Specifies  the standard target. After doing the MAC redirect, the rule still has to
              give a standard target so ebtables knows what to do.  The default target is ACCEPT.
              Making  it CONTINUE could let you use multiple target extensions on the same frame.
              Making it DROP in the BROUTING chain will let the frames be routed. RETURN is  also
              allowed. Note that using RETURN in a base chain is not allowed.

   snat
       The  snat target can only be used in the POSTROUTING chain of the nat table.  It specifies
       that the source MAC address has to be changed.

       --to-source address
              Changes the source MAC address to the specified address. The flag  --to-src  is  an
              alias for this option.

       --snat-target target
              Specifies  the  standard target. After doing the snat, the rule still has to give a
              standard target so ebtables knows what to do.  The default target is ACCEPT. Making
              it  CONTINUE could let you use multiple target extensions on the same frame. Making
              it DROP doesn't make sense, but you could do that too. RETURN is also allowed. Note
              that using RETURN in a base chain is not allowed.

       --snat-arp
              Also  change  the hardware source address inside the arp header if the packet is an
              arp message and the hardware address length in the arp header is 6 bytes.

FILES

       /etc/ethertypes /run/ebtables.lock

ENVIRONMENT VARIABLES

       EBTABLES_ATOMIC_FILE

MAILINGLISTS

       See http://netfilter.org/mailinglists.html

SEE ALSO

       iptables(8), brctl(8), ifconfig(8), route(8)

       See http://ebtables.sf.net

                                          December 2011                               EBTABLES(8)