man > arptables(8)

ARPTABLES(8)                           System Manager's Manual                          ARPTABLES(8)

NAME
       arptables - ARP table administration (nft-based)

SYNOPSIS
       arptables [-t table] -[AD] chain rule-specification [options]
       arptables [-t table] -[RI] chain rulenum rule-specification [options]
       arptables [-t table] -D chain rulenum [options]
       arptables [-t table] -[LFZ] [chain] [options]
       arptables [-t table] -[NX] chain
       arptables [-t table] -E old-chain-name new-chain-name
       arptables [-t table] -P chain target [options]


DESCRIPTION
       arptables  is a user space tool, it is used to set up and maintain the tables of ARP rules in
       the Linux kernel. These rules inspect the ARP frames which they see.  arptables is  analogous
       to the iptables user space tool, but arptables is less complicated.


   CHAINS
       The  kernel  table  is 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  ARP  frames.
       If  a  rule  matches an ARP 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 which can be used as the 'target' of a
       rule.


   TARGETS
       A firewall rule specifies criteria for an ARP 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 user-defined chain.

       ACCEPT  means  to  let  the frame through.  DROP means the frame has to be dropped.  CONTINUE
       means the next rule has to be checked. This can be handy to know how many frames pass a  cer‐
       tain  point in the chain or to log those frames.  RETURN means stop traversing this chain and
       resume at the next rule in the previous (calling) chain.  For the  extension  targets  please
       see the TARGET EXTENSIONS section of this man page.

   TABLES
       There  is only one ARP table in the Linux kernel.  The table is filter.  You can drop the '-t
       filter' argument to the arptables command.  The -t argument must be the first argument on the
       arptables command line, if used.

       -t, --table
              filter, is the only table and contains two built-in chains: INPUT (for frames destined
              for the host) and OUTPUT (for locally-generated frames).

ARPTABLES COMMAND LINE ARGUMENTS
       After the initial arptables command line argument, the remaining  arguments  can  be  divided
       into several different groups.  These groups are commands, miscellaneous commands, rule-spec‐
       ifications, match-extensions, and watcher-extensions.

   COMMANDS
       The  arptables 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.  With the exception of the -Z command, only one command may be used on
       the command line at a time.

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

       -D, --delete
              Delete the specified rule from the selected chain. There are two ways to use this com‐
              mand. The first is by specifying an  interval  of  rule  numbers  to  delete,  syntax:
              start_nr[:end_nr].  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.

       -I, --insert
              Insert  the  specified  rule into the selected chain at the specified rule number.  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 number 0 specifies  the  place  past  the
              last rule in the chain and using this number is therefore equivalent with using the -A
              command.

       -R, --replace
              Replaces  the specified rule into the selected chain at the specified rule number.  If
              the current number of rules equals N, then the specified number can be between  1  and
              N. i specifies the place in the chain where the rule should be replaced.

       -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 the 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 coun‐
              ters  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.

       -N, --new-chain
              Create a new user-defined chain with the given name. The number of user-defined chains
              is unlimited. A user-defined chain name has maximum length of 31 characters.

       -X, --delete-chain
              Delete  the specified user-defined chain. There must be no remaining references to the
              specified chain, otherwise arptables will refuse to delete it. If no chain  is  speci‐
              fied, 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
              may rename a standard chain name to a name that suits your taste. For example, if  you
              like  PREBRIDGING  more than PREROUTING, then you can use the -E command to rename the
              PREROUTING chain. If you do rename one of the standard arptables chain  names,  please
              be  sure  to  mention  this  fact  should you post a question on the arptables mailing
              lists.  It would be wise to use the standard name in your post.  Renaming  a  standard
              arptables  chain  in  this  fashion  has no effect on the structure or function of the
              arptables kernel table.


   MISCELLANEOUS COMMANDS
       -V, --version
              Show the version of the arptables userspace program.

       -h, --help
              Give a brief description of the command syntax.

       -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.

       -c, --set-counters PKTS BYTES
              This  enables  the  administrator to initialize the packet and byte counters of a rule
              (during INSERT, APPEND, REPLACE operations).


   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 specifica‐
       tion. Apart from these standard rule specifications there are some other command  line  argu‐
       ments of interest.

       -s, --source-ip [!] address[/mask]
              The Source IP specification.

       -d, --destination-ip [!] address[/mask]
              The Destination IP specification.

       --source-mac [!] address[/mask]
              The  source  mac  address.  Both mask and address are written as 6 hexadecimal numbers
              separated by colons.

       --destination-mac [!] address[/mask]
              The destination mac address. Both mask and address are written as 6  hexadecimal  num‐
              bers separated by colons.

       -i, --in-interface [!] name
              The interface via which a frame is received (for the INPUT chain). The flag --in-if is
              an alias for this option.

       -o, --out-interface [!] name
              The  interface  via which a frame is going to be sent (for the OUTPUT chain). The flag
              --out-if is an alias for this option.

       -l, --h-length length[/mask]
              The hardware length (nr of bytes)

       --opcode code[/mask]
              The operation code (2 bytes). Available values are:  1=Request  2=Reply  3=Request_Re‐
              verse  4=Reply_Reverse  5=DRARP_Request  6=DRARP_Reply  7=DRARP_Error  8=InARP_Request
              9=ARP_NAK.

       --h-type type[/mask]
              The hardware type (2 bytes, hexadecimal). Available values are: 1=Ethernet.

       --proto-type type[/mask]
              The protocol type (2 bytes). Available values are: 0x800=IPv4.


   TARGET-EXTENSIONS
       arptables extensions are precompiled into the userspace tool. So there is no need to  explic‐
       itly  load them with a -m option like in iptables.  However, these extensions deal with func‐
       tionality supported by supplemental kernel modules.

   mangle
       --mangle-ip-s IP address
              Mangles Source IP Address to given value.

       --mangle-ip-d IP address
              Mangles Destination IP Address to given value.

       --mangle-mac-s MAC address
              Mangles Source MAC Address to given value.

       --mangle-mac-d MAC address
              Mangles Destination MAC Address to given value.

       --mangle-target target
              Target of ARP mangle operation (DROP, CONTINUE or ACCEPT -- default is ACCEPT).

   CLASSIFY
       This  module  allows you to set the skb->priority value (and thus clas- sify the packet  into
       a specific CBQ class).


       --set-class major:minor

              Set  the major and minor  class  value.  The  values  are  always interpreted as hexa‐
              decimal even if no 0x prefix is given.


   MARK
       This  module  allows you to set the skb->mark value (and thus classify the packet by the mark
       in u32)


       --set-mark mark
              Set the mark value. The  values  are  always interpreted as hexadecimal even if no  0x
              prefix is given


       --and-mark mark
              Binary AND the mark with bits.


       --or-mark mark
              Binary OR the mark with bits.


NOTES
       In  this  nft-based version of arptables, support for FORWARD chain has not been implemented.
       Since ARP packets are "forwarded" only by Linux bridges, the same may be achieved using  FOR‐
       WARD chain in ebtables.


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

SEE ALSO
       xtables-nft(8), iptables(8), ebtables(8), ip(8)

       See https://wiki.nftables.org

                                             March 2019                                 ARPTABLES(8)