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RedHat 9 (Linux i386) - man page for ip6tables (redhat section 8)

IP6TABLES(8)									     IP6TABLES(8)

NAME
       ip6tables - IPv6 packet filter administration

SYNOPSIS
       ip6tables [-t table] -[ADC] chain rule-specification [options]
       ip6tables [-t table] -I chain [rulenum] rule-specification [options]
       ip6tables [-t table] -R chain rulenum rule-specification [options]
       ip6tables [-t table] -D chain rulenum [options]
       ip6tables [-t table] -[LFZ] [chain] [options]
       ip6tables [-t table] -N chain
       ip6tables [-t table] -X [chain]
       ip6tables [-t table] -P chain target [options]
       ip6tables [-t table] -E old-chain-name new-chain-name

DESCRIPTION
       Ip6tables  is used to set up, maintain, and inspect the tables of IPv6 packet filter rules
       in the Linux kernel.  Several different tables may be defined.  Each table contains a num-
       ber 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 the 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 or one
       of the special values ACCEPT, DROP, QUEUE, or RETURN.

       ACCEPT means to let the packet through.	DROP means to  drop  the  packet  on  the  floor.
       QUEUE  means  to  pass the packet to userspace (if supported by the kernel).  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 two independent tables (which tables are present at any  time  depends
       on  the	kernel configuration options and which modules are present), as nat table has not
       been implemented yet.

       -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 coming into the box itself), FORWARD (for packets being
	      routed through the box), and OUTPUT (for locally-generated packets).

       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).

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

   COMMANDS
       These  options  specify the specific action to perform.	Only one of them can be specified
       on the command line unless otherwise specified below.  For all the long	versions  of  the
       command and option names, you need to use only enough letters to ensure that ip6tables 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.

       -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
	      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.  As 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
	       ip6tables -L -v

       -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]
	      Zero the packet and byte counters in all chains.	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.	 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 section TARGETS for  the
	      legal targets.  Only built-in (non-user-defined) chains can have policies, and nei-
	      ther 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).

       -p, --protocol [!] protocol
	      The protocol of the rule or of the packet to check.  The specified protocol can  be
	      one of tcp, udp, ipv6-icmp|icmpv6, or all, or it can be a numeric value, represent-
	      ing 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.  Protocol all will match with all protocols and is taken
	      as default when this option is omitted.

       -s, --source [!] address[/mask]
	      Source  specification.  Address can be either a hostname (please note that specify-
	      ing any name to be resolved with a remote query such as DNS is a really bad  idea),
	      a  network  IPv6	address (with /mask), or a plain IPv6 address.	(the network name
	      isn't supported now).  The mask can be either a network mask  or	a  plain  number,
	      specifying the number of 1's at the left side of the network mask.  Thus, a mask of
	      64 is equivalent to ffff:ffff:ffff:ffff:0000:0000:0000:0000.  A "!" argument before
	      the  address  specification  inverts the sense of the address. The flag --src is an
	      alias for this option.

       -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.

       -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, then match-
	      ing the rule will have no effect on the packet's fate, but the counters on the rule
	      will be incremented.

       -i, --in-interface [!] name
	      Name of an interface via which a packet is going to be 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 and OUTPUT chains).  When the "!" argument is used before the interface
	      name, the sense is inverted.  If the interface name ends in a "+", then any  inter-
	      face which begins with this name will match.  If this option is omitted, any inter-
	      face name will match.

       -c, --set-counters  PKTS 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 mul-
	      tipliers respectively (but see the -x flag to change this).  For appending,  inser-
	      tion,  deletion  and  replacement,  this causes detailed information on the rule or
	      rules to be printed.

       -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 mod-
	      ules (targets, match extensions, etc).

MATCH EXTENSIONS
       ip6tables can use extended packet matching modules.  These are loaded in two ways: implic-
       itly,  when  -p or --protocol is specified, or with the -m or --match options, followed by
       the matching module name; after these, various extra command line  options  become  avail-
       able,  depending  on the specific module.  You can specify multiple extended match modules
       in one line, and you can use the -h or --help options after the module has been	specified
       to receive help specific to that module.

       The  following  are included in the base package, and most of these can be preceded by a !
       to invert the sense of the match.

   tcp
       These extensions are loaded if `--protocol tcp' is specified. It  provides  the	following
       options:

       --source-port [!] port[:port]
	      Source  port  or	port  range specification. This can either be a service name or a
	      port number. An inclusive range can also be specified, using the format  port:port.
	      If  the  first  port is omitted, "0" is assumed; if the last is omitted, "65535" is
	      assumed.	If the second port greater then the first they will be swapped.  The flag
	      --sport is a convenient alias for this option.

       --destination-port [!] port[:port]
	      Destination  port  or  port  range specification.  The flag --dport is a convenient
	      alias for this option.

       --tcp-flags [!] mask comp
	      Match when the TCP flags are as specified.  The first argument is the  flags  which
	      we  should examine, written as a comma-separated list, and the second argument is a
	      comma-separated list of flags which must be set.	Flags are: SYN ACK  FIN  RST  URG
	      PSH ALL NONE.  Hence the command
	       ip6tables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST SYN
	      will  only  match  packets  with	the  SYN flag set, and the ACK, FIN and RST flags
	      unset.

       [!] --syn
	      Only match TCP packets with the SYN bit set and the ACK and FIN bits cleared.  Such
	      packets  are  used to request TCP connection initiation; for example, blocking such
	      packets coming in an interface will prevent incoming TCP connections, but  outgoing
	      TCP  connections	will  be unaffected.  It is equivalent to --tcp-flags SYN,RST,ACK
	      SYN.  If the "!" flag precedes the "--syn", the sense of the option is inverted.

       --tcp-option [!] number
	      Match if TCP option set.

   udp
       These extensions are loaded if `--protocol udp' is specified.  It provides  the	following
       options:

       --source-port [!] port[:port]
	      Source  port or port range specification.  See the description of the --source-port
	      option of the TCP extension for details.

       --destination-port [!] port[:port]
	      Destination port or port range specification.  See the description of the  --desti-
	      nation-port option of the TCP extension for details.

   ipv6-icmp
       This extension is loaded if `--protocol ipv6-icmp' or `--protocol icmpv6' is specified. It
       provides the following option:

       --icmpv6-type [!] typename
	      This allows specification of the ICMP type, which can be a numeric IPv6-ICMP  type,
	      or one of the IPv6-ICMP type names shown by the command
	       ip6tables -p ipv6-icmp -h

   mac
       --mac-source [!] address
	      Match  source  MAC  address.   It must be of the form XX:XX:XX:XX:XX:XX.	Note that
	      this only makes sense for packets coming from an Ethernet device and  entering  the
	      PREROUTING, FORWARD or INPUT chains.

   limit
       This  module  matches  at  a  limited rate using a token bucket filter.	A rule using this
       extension will match until this limit is reached (unless the `!' flag is used).	It can be
       used in combination with the LOG target to give limited logging, for example.

       --limit rate
	      Maximum  average	matching rate: specified as a number, with an optional `/second',
	      `/minute', `/hour', or `/day' suffix; the default is 3/hour.

       --limit-burst number
	      Maximum initial number of packets to match: this number gets recharged by one every
	      time the limit specified above is not reached, up to this number; the default is 5.

   multiport
       This  module  matches  a set of source or destination ports.  Up to 15 ports can be speci-
       fied.  It can only be used in conjunction with -p tcp or -p udp.

       --source-ports port[,port[,port...]]
	      Match if the source port is one of the given ports.  The flag --sports is a  conve-
	      nient alias for this option.

       --destination-ports port[,port[,port...]]
	      Match  if  the  destination port is one of the given ports.  The flag --dports is a
	      convenient alias for this option.

       --ports port[,port[,port...]]
	      Match if the both the source and destination ports are equal to each other  and  to
	      one of the given ports.

   mark
       This  module  matches  the netfilter mark field associated with a packet (which can be set
       using the MARK target below).

       --mark value[/mask]
	      Matches packets with the given unsigned mark value (if a mask is specified, this is
	      logically ANDed with the mask before the comparison).

   owner
       This  module attempts to match various characteristics of the packet creator, for locally-
       generated packets.  It is only valid in the OUTPUT chain, and even this some packets (such
       as  ICMP  ping  responses)  may have no owner, and hence never match.  This is regarded as
       experimental.

       --uid-owner userid
	      Matches if the packet was created by a process with the given effective user id.

       --gid-owner groupid
	      Matches if the packet was created by a process with the given effective group id.

       --pid-owner processid
	      Matches if the packet was created by a process with the given process id.

       --sid-owner sessionid
	      Matches if the packet was created by a process in the given session group.

TARGET EXTENSIONS
       ip6tables can use extended target modules: the following are included in the standard dis-
       tribution.

   LOG
       Turn on kernel logging of matching packets.  When this option is set for a rule, the Linux
       kernel will print some information on all matching packets  (like  most	IPv6  IPv6-header
       fields)	via  the  kernel  log (where it can be read with dmesg or syslogd(8)).	This is a
       "non-terminating target", i.e. rule traversal continues at the next rule.  So if you  want
       to  LOG	the  packets  you refuse, use two separate rules with the same matching criteria,
       first using target LOG then DROP (or REJECT).

       --log-level level
	      Level of logging (numeric or see syslog.conf(5)).

       --log-prefix prefix
	      Prefix log messages with the specified prefix; up to 29 letters  long,  and  useful
	      for distinguishing messages in the logs.

       --log-tcp-sequence
	      Log TCP sequence numbers. This is a security risk if the log is readable by users.

       --log-tcp-options
	      Log options from the TCP packet header.

       --log-ip-options
	      Log options from the IPv6 packet header.

   MARK
       This is used to set the netfilter mark value associated with the packet.  It is only valid
       in the mangle table.

       --set-mark mark

   REJECT
       This is used to send back an error packet in response to the matched packet: otherwise  it
       is  equivalent  to DROP so it is a terminating TARGET, ending rule traversal.  This target
       is only valid in the INPUT, FORWARD and OUTPUT chains, and user-defined chains  which  are
       only  called  from  those  chains.   The following option controls the nature of the error
       packet returned:

       --reject-with type
	      The type given can be icmp6-no-route, no-route,  icmp6-adm-prohibited,  adm-prohib-
	      ited,  icmp6-addr-unreachable,  addr-unreach, icmp6-port-unreachable, port-unreach,
	      which return the appropriate IPv6-ICMP error message (port-unreach is the default).
	      Finally,	the option tcp-reset can be used on rules which only match the TCP proto-
	      col: this causes a TCP RST packet to be sent  back.   This  is  mainly  useful  for
	      blocking	ident (113/tcp) probes which frequently occur when sending mail to broken
	      mail hosts (which won't accept your mail otherwise).

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 parame-
       ters cause an exit code of 2, and other errors cause an exit code of 1.

BUGS
       Bugs?  What's this? ;-) Well... the counters are not reliable on sparc64.

COMPATIBILITY WITH IPCHAINS
       This ip6tables 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; 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 out-
       put interface, and both are available for packets entering the FORWARD chain.   There  are
       several other changes in ip6tables.

SEE ALSO
       ip6tables-save(8),    ip6tables-restore(8),   iptables(8),   iptables-save(8),	iptables-
       restore(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 wrote iptables, in early consultation with Michael Neuling.

       Marc Boucher made Rusty abandon ipnatctl by lobbying for a generic packet selection frame-
       work  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 target, TTL match+target and libipulog.

       The Netfilter Core Team is: Marc Boucher, Jozsef Kadlecsik, James Morris, Harald Welte and
       Rusty Russell.

       ip6tables  man  page  created  by  Andras Kis-Szabo, based on iptables man page written by
       Herve Eychenne <rv@wallfire.org>.

					   Mar 09, 2002 			     IP6TABLES(8)


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