iptables man page on Kali

Man page or keyword search:  
man Server   9211 pages
apropos Keyword Search (all sections)
Output format
Kali logo
[printable version]

IPTABLES(8)			iptables 1.6.1			   IPTABLES(8)

NAME
       iptables/ip6tables — administration tool for IPv4/IPv6 packet filtering
       and NAT

SYNOPSIS
       iptables [-t table] {-A|-C|-D} chain rule-specification

       ip6tables [-t table] {-A|-C|-D} chain rule-specification

       iptables [-t table] -I chain [rulenum] rule-specification

       iptables [-t table] -R chain rulenum rule-specification

       iptables [-t table] -D chain rulenum

       iptables [-t table] -S [chain [rulenum]]

       iptables [-t table] {-F|-L|-Z} [chain [rulenum]] [options...]

       iptables [-t table] -N chain

       iptables [-t table] -X [chain]

       iptables [-t table] -P chain target

       iptables [-t table] -E old-chain-name new-chain-name

       rule-specification = [matches...] [target]

       match = -m matchname [per-match-options]

       target = -j targetname [per-target-options]

DESCRIPTION
       Iptables and ip6tables are used to set up, maintain,  and  inspect  the
       tables  of IPv4 and IPv6 packet filter rules in the Linux kernel.  Sev‐
       eral different tables may be defined.  Each table contains a number  of
       built-in chains and may also contain user-defined chains.

       Each  chain  is a list of rules which can match a set of packets.  Each
       rule specifies what to do with a packet that matches.  This is called a
       `target',  which	 may be a jump to a user-defined chain in the same ta‐
       ble.

TARGETS
       A firewall rule specifies criteria for a packet and a target.   If  the
       packet  does  not  match, the next rule in the chain is examined; if it
       does match, then the next rule is specified by the value of the target,
       which  can  be  the  name  of  a user-defined chain, one of the targets
       described in iptables-extensions(8),  or	 one  of  the  special	values
       ACCEPT, DROP or RETURN.

       ACCEPT  means to let the packet through.	 DROP means to drop the packet
       on the floor.  RETURN means stop traversing this chain  and  resume  at
       the  next rule in the previous (calling) chain.	If the end of a built-
       in chain is reached or a rule in a built-in chain with target RETURN is
       matched,	 the  target specified by the chain policy determines the fate
       of the packet.

TABLES
       There are currently five independent tables (which tables  are  present
       at  any time depends on the kernel configuration options and which mod‐
       ules are present).

       -t, --table table
	      This option specifies the packet matching table which  the  com‐
	      mand  should operate on.	If the kernel is configured with auto‐
	      matic module loading, an attempt will be made to load the appro‐
	      priate module for that table if it is not already there.

	      The tables are as follows:

	      filter:
		  This	is  the	 default table (if no -t option is passed). It
		  contains the built-in chains INPUT (for packets destined  to
		  local	 sockets),  FORWARD  (for packets being routed through
		  the box), and OUTPUT (for locally-generated packets).

	      nat:
		  This table is consulted when a packet	 that  creates	a  new
		  connection  is  encountered.	It consists of four built-ins:
		  PREROUTING (for altering packets as soon as they  come  in),
		  INPUT	 (for  altering	 packets  destined for local sockets),
		  OUTPUT (for altering locally-generated packets before	 rout‐
		  ing),	 and  POSTROUTING  (for	 altering  packets as they are
		  about to go out).  IPv6 NAT support is available since  ker‐
		  nel 3.7.

	      mangle:
		  This table is used for specialized packet alteration.	 Until
		  kernel 2.4.17 it had two built-in  chains:  PREROUTING  (for
		  altering  incoming  packets  before routing) and OUTPUT (for
		  altering locally-generated packets before  routing).	 Since
		  kernel  2.4.18,  three  other	 built-in chains are also sup‐
		  ported: INPUT (for packets coming into the box itself), FOR‐
		  WARD	(for  altering	packets being routed through the box),
		  and POSTROUTING (for altering packets as they are  about  to
		  go out).

	      raw:
		  This	table  is  used mainly for configuring exemptions from
		  connection tracking in combination with the NOTRACK  target.
		  It registers at the netfilter hooks with higher priority and
		  is thus called before ip_conntrack, or any other IP  tables.
		  It  provides	the following built-in chains: PREROUTING (for
		  packets arriving via	any  network  interface)  OUTPUT  (for
		  packets generated by local processes)

	      security:
		  This	table  is used for Mandatory Access Control (MAC) net‐
		  working rules, such as those	enabled	 by  the  SECMARK  and
		  CONNSECMARK  targets.	  Mandatory  Access  Control is imple‐
		  mented by Linux Security Modules such as SELinux.  The secu‐
		  rity	table  is  called after the filter table, allowing any
		  Discretionary Access Control (DAC) rules in the filter table
		  to  take  effect  before MAC rules.  This table provides the
		  following built-in chains: INPUT (for	 packets  coming  into
		  the  box  itself),  OUTPUT  (for  altering locally-generated
		  packets before routing), and FORWARD (for  altering  packets
		  being routed through the box).

OPTIONS
       The  options  that  are	recognized  by	iptables  and ip6tables can be
       divided into several different groups.

   COMMANDS
       These options specify the desired action to perform. Only one  of  them
       can be specified on the command line unless otherwise stated below. For
       long versions of the command and option names, you  need	 to  use  only
       enough  letters	to  ensure that iptables can differentiate it from all
       other options.

       -A, --append chain rule-specification
	      Append one or more rules to the end of the selected chain.  When
	      the  source  and/or  destination	names resolve to more than one
	      address, a rule will be added for each possible address combina‐
	      tion.

       -C, --check chain rule-specification
	      Check  whether  a	 rule matching the specification does exist in
	      the selected chain. This command uses the same logic  as	-D  to
	      find  a matching entry, but does not alter the existing iptables
	      configuration and uses its exit  code  to	 indicate  success  or
	      failure.

       -D, --delete chain rule-specification
       -D, --delete chain rulenum
	      Delete one or more rules from the selected chain.	 There are two
	      versions of this command: the rule can be specified as a	number
	      in  the  chain  (starting	 at 1 for the first rule) or a rule to
	      match.

       -I, --insert chain [rulenum] rule-specification
	      Insert one or more rules in the selected chain as the given rule
	      number.	So,  if	 the  rule  number is 1, the rule or rules are
	      inserted at the head of the chain.  This is also the default  if
	      no rule number is specified.

       -R, --replace chain rulenum rule-specification
	      Replace a rule in the selected chain.  If the source and/or des‐
	      tination names resolve to multiple addresses, the	 command  will
	      fail.  Rules are numbered starting at 1.

       -L, --list [chain]
	      List  all rules in the selected chain.  If no chain is selected,
	      all chains are listed. Like every	 other	iptables  command,  it
	      applies  to  the specified table (filter is the default), so NAT
	      rules get listed by
	       iptables -t nat -n -L
	      Please note that it is often used with the -n option,  in	 order
	      to  avoid	 long reverse DNS lookups.  It is legal to specify the
	      -Z (zero) option as well, in which case  the  chain(s)  will  be
	      atomically  listed  and zeroed.  The exact output is affected by
	      the other arguments given. The exact rules are suppressed	 until
	      you use
	       iptables -L -v
	      or iptables-save(8).

       -S, --list-rules [chain]
	      Print all rules in the selected chain.  If no chain is selected,
	      all chains are printed like iptables-save. Like every other ipt‐
	      ables  command, it applies to the specified table (filter is the
	      default).

       -F, --flush [chain]
	      Flush the selected chain (all the chains in the table if none is
	      given).	This  is  equivalent  to deleting all the rules one by
	      one.

       -Z, --zero [chain [rulenum]]
	      Zero the packet and byte counters in all	chains,	 or  only  the
	      given  chain,  or only the given rule in a chain. It is legal to
	      specify the -L, --list (list) option as well, to see  the	 coun‐
	      ters immediately before they are cleared. (See above.)

       -N, --new-chain chain
	      Create  a	 new user-defined chain by the given name.  There must
	      be no target of that name already.

       -X, --delete-chain [chain]
	      Delete the optional user-defined chain specified.	 There must be
	      no  references  to  the chain.  If there are, you must delete or
	      replace the referring rules before the  chain  can  be  deleted.
	      The  chain  must	be  empty,  i.e. not contain any rules.	 If no
	      argument is given, it will attempt to delete  every  non-builtin
	      chain in the table.

       -P, --policy chain target
	      Set  the policy for the built-in (non-user-defined) chain to the
	      given target.  The policy target must be either ACCEPT or DROP.

       -E, --rename-chain old-chain new-chain
	      Rename the user specified chain to the user supplied name.  This
	      is cosmetic, and has no effect on the structure of the table.

       -h     Help.   Give a (currently very brief) description of the command
	      syntax.

   PARAMETERS
       The following parameters make up a rule specification (as used  in  the
       add, delete, insert, replace and append commands).

       -4, --ipv4
	      This  option has no effect in iptables and iptables-restore.  If
	      a rule using the -4 option is  inserted  with  (and  only	 with)
	      ip6tables-restore,  it  will be silently ignored. Any other uses
	      will throw an error. This option allows IPv4 and IPv6 rules in a
	      single   rule  file  for	use  with  both	 iptables-restore  and
	      ip6tables-restore.

       -6, --ipv6
	      If a rule using the -6 option is inserted with (and  only	 with)
	      iptables-restore,	 it  will  be silently ignored. Any other uses
	      will throw an error. This option allows IPv4 and IPv6 rules in a
	      single   rule  file  for	use  with  both	 iptables-restore  and
	      ip6tables-restore.  This option has no effect in	ip6tables  and
	      ip6tables-restore.

       [!] -p, --protocol protocol
	      The  protocol of the rule or of the packet to check.  The speci‐
	      fied protocol can be one of tcp, udp, udplite, icmp, icmpv6,esp,
	      ah,  sctp,  mh  or  the  special	keyword	 "all", or it can be a
	      numeric value, representing one of these protocols or a  differ‐
	      ent  one.	  A protocol name from /etc/protocols is also allowed.
	      A "!" argument before the protocol inverts the test.  The number
	      zero  is	equivalent to all. "all" will match with all protocols
	      and is taken as default when this option is omitted.  Note that,
	      in ip6tables, IPv6 extension headers except esp are not allowed.
	      esp and ipv6-nonext can be used with Kernel  version  2.6.11  or
	      later.   The  number zero is equivalent to all, which means that
	      you cannot test the protocol field for the value 0 directly.  To
	      match  on a HBH header, even if it were the last, you cannot use
	      -p 0, but always need -m hbh.

       [!] -s, --source address[/mask][,...]
	      Source specification. Address can be either a  network  name,  a
	      hostname,	 a  network  IP	 address  (with	 /mask), or a plain IP
	      address. Hostnames will be resolved once only, before  the  rule
	      is  submitted  to	 the  kernel.  Please note that specifying any
	      name to be resolved with a remote query such as DNS is a	really
	      bad idea.	 The mask can be either an ipv4 network mask (for ipt‐
	      ables) or a plain number, specifying the number of  1's  at  the
	      left  side of the network mask.  Thus, an iptables mask of 24 is
	      equivalent to 255.255.255.0.  A "!" argument before the  address
	      specification  inverts  the sense of the address. The flag --src
	      is an alias for this option.  Multiple addresses can  be	speci‐
	      fied,  but  this will expand to multiple rules (when adding with
	      -A), or will cause multiple rules to be deleted (with -D).

       [!] -d, --destination address[/mask][,...]
	      Destination  specification.   See	 the  description  of  the  -s
	      (source)	flag  for  a  detailed description of the syntax.  The
	      flag --dst is an alias for this option.

       -m, --match match
	      Specifies a match to use, that  is,  an  extension  module  that
	      tests  for  a  specific property. The set of matches make up the
	      condition under which a target is invoked. Matches are evaluated
	      first  to	 last  as  specified  on  the command line and work in
	      short-circuit fashion, i.e. if one extension yields false, eval‐
	      uation will stop.

       -j, --jump target
	      This  specifies  the target of the rule; i.e., what to do if the
	      packet matches it.  The  target  can  be	a  user-defined	 chain
	      (other than the one this rule is in), one of the special builtin
	      targets which decide the fate of the packet immediately,	or  an
	      extension	 (see EXTENSIONS below).  If this option is omitted in
	      a rule (and -g is not used), then matching the rule will have no
	      effect  on  the packet's fate, but the counters on the rule will
	      be incremented.

       -g, --goto chain
	      This specifies that the processing should	 continue  in  a  user
	      specified	 chain.	 Unlike the --jump option return will not con‐
	      tinue processing in this chain but instead  in  the  chain  that
	      called us via --jump.

       [!] -i, --in-interface name
	      Name  of	an interface via which a packet was received (only for
	      packets entering the  INPUT,  FORWARD  and  PREROUTING  chains).
	      When  the	 "!"  argument	is used before the interface name, the
	      sense is inverted.  If the interface name ends in	 a  "+",  then
	      any  interface  which begins with this name will match.  If this
	      option is omitted, any interface name will match.

       [!] -o, --out-interface name
	      Name of an interface via which a packet is going to be sent (for
	      packets  entering	 the  FORWARD, OUTPUT and POSTROUTING chains).
	      When the "!" argument is used before  the	 interface  name,  the
	      sense  is	 inverted.   If the interface name ends in a "+", then
	      any interface which begins with this name will match.   If  this
	      option is omitted, any interface name will match.

       [!] -f, --fragment
	      This  means that the rule only refers to second and further IPv4
	      fragments of fragmented packets.	Since there is no way to  tell
	      the source or destination ports of such a packet (or ICMP type),
	      such a packet will not match any rules which specify them.  When
	      the  "!"	argument  precedes  the	 "-f" flag, the rule will only
	      match head fragments, or unfragmented packets.  This  option  is
	      IPv4 specific, it is not available in ip6tables.

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

   OTHER OPTIONS
       The following additional options can be specified:

       -v, --verbose
	      Verbose output.  This option makes the  list  command  show  the
	      interface	 name,	the  rule options (if any), and the TOS masks.
	      The packet and byte counters are also listed,  with  the	suffix
	      'K',  'M' or 'G' for 1000, 1,000,000 and 1,000,000,000 multipli‐
	      ers respectively (but see the -x	flag  to  change  this).   For
	      appending,  insertion,  deletion	and  replacement,  this causes
	      detailed information on the rule or rules to be printed. -v  may
	      be specified multiple times to possibly emit more detailed debug
	      statements.

       -w, --wait [seconds]
	      Wait for the xtables lock.  To prevent multiple instances of the
	      program  from  running  concurrently, an attempt will be made to
	      obtain an exclusive lock at launch.   By	default,  the  program
	      will exit if the lock cannot be obtained.	 This option will make
	      the program wait (indefinitely or for  optional  seconds)	 until
	      the exclusive lock can be obtained.

       -W, --wait-interval microseconds
	      Interval	to wait per each iteration.  When running latency sen‐
	      sitive applications, waiting for the xtables lock	 for  extended
	      durations	 may  not  be  acceptable.  This option will make each
	      iteration take the amount of time specified. The default	inter‐
	      val is 1 second. This option only works with -w.

       -n, --numeric
	      Numeric  output.	 IP addresses and port numbers will be printed
	      in numeric format.  By default, the program will try to  display
	      them  as host names, network names, or services (whenever appli‐
	      cable).

       -x, --exact
	      Expand numbers.  Display the exact value of the packet and  byte
	      counters,	 instead  of only the rounded number in K's (multiples
	      of 1000) M's (multiples of 1000K) or G's (multiples  of  1000M).
	      This option is only relevant for the -L command.

       --line-numbers
	      When  listing  rules,  add line numbers to the beginning of each
	      rule, corresponding to that rule's position in the chain.

       --modprobe=command
	      When adding or inserting rules into a chain, use command to load
	      any necessary modules (targets, match extensions, etc).

MATCH AND TARGET EXTENSIONS
       iptables	 can  use extended packet matching and target modules.	A list
       of these is available in the iptables-extensions(8) manpage.

DIAGNOSTICS
       Various error messages are printed to standard error.  The exit code is
       0 for correct functioning.  Errors which appear to be caused by invalid
       or abused command line parameters cause an exit code of	2,  and	 other
       errors cause an exit code of 1.

BUGS
       Bugs?   What's  this?  ;-)  Well,  you  might  want  to	have a look at
       http://bugzilla.netfilter.org/

COMPATIBILITY WITH IPCHAINS
       This iptables is very similar to ipchains by Rusty Russell.   The  main
       difference  is  that the chains INPUT and OUTPUT are only traversed for
       packets coming into the local host and originating from the local  host
       respectively.   Hence every packet only passes through one of the three
       chains (except loopback traffic, which involves both INPUT  and	OUTPUT
       chains); previously a forwarded packet would pass through all three.

       The  other main difference is that -i refers to the input interface; -o
       refers to the output interface, and  both  are  available  for  packets
       entering the FORWARD chain.

       The  various  forms  of NAT have been separated out; iptables is a pure
       packet filter when using the  default  `filter'	table,	with  optional
       extension modules.  This should simplify much of the previous confusion
       over the combination of IP masquerading and packet filtering seen  pre‐
       viously.	 So the following options are handled differently:
	-j MASQ
	-M -S
	-M -L
       There are several other changes in iptables.

SEE ALSO
       iptables-apply(8),    iptables-save(8),	  iptables-restore(8),	 ipta‐
       bles-extensions(8),

       The packet-filtering-HOWTO details iptables usage for packet filtering,
       the  NAT-HOWTO  details NAT, the netfilter-extensions-HOWTO details the
       extensions that are not in the standard distribution, and  the  netfil‐
       ter-hacking-HOWTO details the netfilter internals.
       See http://www.netfilter.org/.

AUTHORS
       Rusty  Russell  originally  wrote  iptables, in early consultation with
       Michael Neuling.

       Marc Boucher made Rusty abandon ipnatctl	 by  lobbying  for  a  generic
       packet  selection  framework  in iptables, then wrote the mangle table,
       the owner match, the mark stuff, and ran around doing cool stuff every‐
       where.

       James Morris wrote the TOS target, and tos match.

       Jozsef Kadlecsik wrote the REJECT target.

       Harald  Welte  wrote  the  ULOG and NFQUEUE target, the new libiptc, as
       well as the TTL, DSCP, ECN matches and targets.

       The Netfilter Core Team is: Jozsef Kadlecsik,  Patrick  McHardy,	 Pablo
       Neira Ayuso, Eric Leblond and Florian Westphal. Emeritus Core Team mem‐
       bers are: Marc Boucher, Martin Josefsson, Yasuyuki Kozakai, James  Mor‐
       ris, Harald Welte and Rusty Russell.

       Man page originally written by Herve Eychenne <rv@wallfire.org>.

VERSION
       This manual page applies to iptables/ip6tables 1.6.1.

iptables 1.6.1							   IPTABLES(8)
[top]

List of man pages available for Kali

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net