IP6TABLES(8) iptables 1.4.19.1 IP6TABLES(8)NAME
ip6tables — IPv6 packet filter administration
SYNOPSIS
ip6tables [-t table] {-A|-C|-D} 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] -S [chain [rulenum]]
ip6tables [-t table] {-F|-L|-Z} [chain [rulenum]] [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 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 the examined; if
it does match, then the next rule is specified by the value of the tar‐
get, which can be the name of a user-defined chain or one of the spe‐
cial 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. (How the
packet can be received by a userspace process differs by the particular
queue handler. 2.4.x and 2.6.x kernels up to 2.6.13 include the
ip_queue queue handler. Kernels 2.6.14 and later additionally include
the nfnetlink_queue queue handler. Packets with a target of QUEUE will
be sent to queue number '0' in this case. Please also see the NFQUEUE
target as described later in this man page.) 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). 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 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 ip6tables can be divided into sev‐
eral 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 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 ip6tables command, it
applies to the specified table (filter is the default).
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
-S, --list-rules [chain]
Print all rules in the selected chain. If no chain is selected,
all chains are printed like ip6tables-save. Like every other
ip6tables 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.
-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.
-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
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 to put both IPv4 and
IPv6 rules in a single rule file for use with both iptables-
restore and ip6tables-restore.
-6, --ipv6
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, icmpv6, esp, mh
or the special keyword "all", or it can be a numeric value, rep‐
resenting one of these protocols or a different one. A protocol
name from /etc/protocols is also allowed. But IPv6 extension
headers except esp are not allowed. esp and ipv6-nonext can be
used with Kernel version 2.6.11 or later. A "!" argument before
the protocol inverts the test. 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. "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 be a hostname, a
network IP address (with /mask), or a plain IP address. Names
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. (Resolv‐
ing network names is not supported at this time.) The mask is a
plain number, specifying the number of 1's at the left side of
the network mask. A "!" argument before the address specifica‐
tion 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, 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.
-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.
-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 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... 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 (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. There are several other changes in
ip6tables.
SEE ALSOip6tables-save(8), ip6tables-restore(8), iptables(8), ipta‐
bles-apply(8), iptables-extensions(8), iptables-save(8), ipta‐
bles-restore(8), libipq(3).
The packet-filtering-HOWTO details iptables usage for packet filtering,
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 Neul‐
ing.
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 TTL match+target and libipulog.
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.
ip6tables man page created by Andras Kis-Szabo, based on iptables man
page written by Herve Eychenne <rv@wallfire.org>.
VERSION
This manual page applies to ip6tables @PACKAGE_VERSION@.
iptables 1.4.19.1IP6TABLES(8)