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IPTABLES(8)			iptables 1.4.21			   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 three built-ins:
		  PREROUTING (for altering packets as soon as they  come  in),
		  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

       -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 chain to the given target.	 See the  sec‐
	      tion  TARGETS  for  the legal targets.  Only built-in (non-user-
	      defined) chains can have	policies,  and	neither	 built-in  nor
	      user-defined chains can be policy targets.

       -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
	      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 until the exclusive lock can be obtained.

       -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: Marc Boucher,  Martin  Josefsson,  Yasuyuki
       Kozakai,	 Jozsef	 Kadlecsik, Patrick McHardy, James Morris, Pablo Neira
       Ayuso, Harald Welte and Rusty Russell.

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

VERSION
       This manual page applies to iptables/ip6tables @PACKAGE_AND_VERSION@.

iptables 1.4.21							   IPTABLES(8)
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