IPTABLES(8)                                           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.  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

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     IPTABLES(8)                                           IPTABLES(8)

          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

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     IPTABLES(8)                                           IPTABLES(8)

                   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) 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

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     IPTABLES(8)                                           IPTABLES(8)

               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

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     IPTABLES(8)                                           IPTABLES(8)

               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 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.

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     IPTABLES(8)                                           IPTABLES(8)

          [!] -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

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     IPTABLES(8)                                           IPTABLES(8)

               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 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:

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     IPTABLES(8)                                           IPTABLES(8)

          -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.

          -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 sensitive 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 interval 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 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).

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     IPTABLES(8)                                           IPTABLES(8)

     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, 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 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),

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     IPTABLES(8)                                           IPTABLES(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 http://www.netfilter.org/.

     AUTHORS
          Rusty Russell originally wrote iptables, in early consulta-
          tion 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 1.8.7.

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