IPTABLES(8)			iptables 1.8.11			   IPTABLES(8)

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

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

       ip6tables [-t table] {-A|-C|-D|-V} 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 policy

       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.
       Several 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
       table.

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
       modules are present).

       -t, --table table
	      This option specifies the packet matching table which the
	      command should operate on.  If the kernel is configured with
	      automatic module loading, an attempt will be made to load the
	      appropriate 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
		  routing), and POSTROUTING (for altering packets as they are
		  about to go out).  IPv6 NAT support is available since
		  kernel 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
		  supported: INPUT (for packets coming into the box itself),
		  FORWARD (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) and OUTPUT (for
		  packets generated by local processes).

	      security:
		  This table is used for Mandatory Access Control (MAC)
		  networking rules, such as those enabled by the SECMARK and
		  CONNSECMARK targets.	Mandatory Access Control is
		  implemented by Linux Security Modules such as SELinux.  The
		  security 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
	      combination.

       -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
	      destination 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
	      iptables 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
	      counters 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 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
	      delete all empty chains in the table. Empty builtin chains can
	      only be deleted with iptables-nft.

       -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
	      specified 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
	      different 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
	      iptables) 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
	      specified, 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,
	      evaluation 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 MATCH AND TARGET 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 with the --jump option, RETURN will not
	      continue 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
	      multipliers 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: Specified twice, iptables-legacy will dump table
	      info and entries in libiptc, iptables-nft dumps rules in netlink
	      (VM code) presentation.  Specified three times, iptables-nft
	      will also dump any netlink messages sent to kernel.

       -V, --version
	      Show program version and the kernel API used.

       -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.

       -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
	      applicable).

       -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).


LOCK FILE
       iptables uses the /run/xtables.lock file to take an exclusive lock at
       launch.

       The XTABLES_LOCKFILE environment variable can be used to override the
       default setting.


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. Errors which
       indicate an incompatibility between kernel and user space cause an exit
       code of 3. Errors which indicate a resource problem, such as a busy
       lock, failing memory allocation or error messages from kernel cause an
       exit code of 4. Finally, other errors cause an exit code of 1.

BUGS
       Bugs?  What's this? ;-) Well, you might want to have a look at
       https://bugzilla.netfilter.org/ iptables will exit immediately with an
       error code of 111 if it finds that it was called as a setuid-to-root
       program.	 iptables cannot be used safely in this manner because it
       trusts the shared libraries (matches, targets) loaded at run time, the
       search path can be set using environment variables.

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 avoid much of the confusion over the
       combination of IP masquerading and packet filtering seen previously.
       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),
       iptables-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
       netfilter-hacking-HOWTO details the netfilter internals.
       See https://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
       everywhere.

       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, Pablo Neira Ayuso, Eric
       Leblond, Florian Westphal and  Arturo Borrero Gonzalez.	Emeritus Core
       Team members are: Marc Boucher, Martin Josefsson, Yasuyuki Kozakai,
       James Morris, Harald Welte and Rusty Russell.

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

VERSION
       This manual page applies to iptables/ip6tables 1.8.11.

iptables 1.8.11							   IPTABLES(8)