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 mangle rules get listed by

 ip6tables -t mangle -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 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.

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, 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. 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 specifying 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 matching 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 interface which begins with this name will match. If this option is omitted, any interface 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).

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.

-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).

This module matches the SPIs in AH header of IPSec packets.

--ahspi [!] spi[:spi]

This matches if a specific /proc filename is '0' or '1'.

--condition [!] filename

Match on boolean value stored in /proc/net/ip6t_condition/filename file

This module matches the IPv6 destination header options

--dst-len[!]length

Total length of this header

--dst-opts TYPE[:LEN],[,TYPE[:LEN]...]

Options and it's length (List).

This module matches the SPIs in ESP header of IPSec packets.

--espspi [!] spi[:spi]

This module matches the EUI64 part of a stateless autoconfigured IPv6 address. It compares the source MAC address with the lower 64 bits of the IPv6 address.

This module matches the time IPv6 fragmentathion header

--fragid [!]id[:id]

Matches the given fragmentation ID (range).

--fraglen [!]length

Matches the total length of this header.

--fragres

Matches the reserved field, too.

--fragfirst

Matches on the first fragment.

[--fragmore]

Matches if there are more fragments.

[--fraglast]

Matches if this is the last fragement.

This module matches a rate limit based on a fuzzy logic controller [FLC]

--lower-limit number"

Specifies the lower limit (in packets per second).

--upper-limit number

Specifies the upper limit (in packets per second).

This module matches the IPv6 hop-by-hop header options

--hbh-len[!]length

Total length of this header

--hbh-opts TYPE[:LEN],[,TYPE[:LEN]...]

Options and it's length (List).

This module matches the HOPLIMIT field in the IPv6 header.

--hl-eq value

Matches if HOPLIMIT equals the given value.

--hl-lt ttl

Matches if HOPLIMIT is less than the given value.

--hl-gt ttl

Matches if HOPLIMIT is greater than the given value.

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

This module matches on IPv6 option headers

--header [!]headers

Matches the given type of headers. Names: hop,dst,route,frag,auth,esp,none,proto Long Names: hop-by-hop,ipv6-opts,ipv6-route,ipv6-frag,ah,esp,ipv6-nonxt,protocol Numbers: 0,60,43,44,51,50,59

--soft

The header CONTAINS the specified extensions.

This module matches the length of a packet against a specific value or range of values.

--length length[:length]

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.

--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.

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).

This module matches a set of source or destination ports. Up to 15 ports can be specified. A port range (port:port) counts as two ports. It can only be used in conjunction with -p tcp or -p udp.

--source-ports [!] port[,port[,port:port...]]

Match if the source port is one of the given ports. The flag --sports is a convenient alias for this option.

--destination-ports [!] port[,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:port...]]

Match if the both the source and destination ports are equal to each other and to one of the given ports.

This module matches every `n'th packet

--every value

Match every `value' packet

[--counter num]

Use internal counter number `num'. Default is `0'.

[--start num]

Initialize the counter at the number `num' insetad of `0'. Most between `0' and `value'-1.

[--packet num]

Match on `num' packet. Most be between `0' and `value'-1.

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.

--cmd-owner name

Matches if the packet was created by a process with the given command name. (this option is present only if iptables was compiled under a kernel supporting this feature)

NOTE: pid, sid and command matching are broken on SMP

This module matches on the bridge port input and output devices enslaved to a bridge device. This module is a part of the infrastructure that enables a transparent bridging IP firewall and is only useful for kernel versions above version 2.5.44.

--physdev-in name

Name of a bridge port via which a packet is received (only for packets entering the INPUT, FORWARD and PREROUTING chains). If the interface name ends in a "+", then any interface which begins with this name will match. If the packet didn't arrive through a bridge device, this packet won't match this option, unless '!' is used.

--physdev-out name

Name of a bridge port via which a packet is going to be sent (for packets entering the FORWARD, OUTPUT and POSTROUTING chains). If the interface name ends in a "+", then any interface which begins with this name will match. Note that in the nat and mangle OUTPUT chains one cannot match on the bridge output port, however one can in the filter OUTPUT chain. If the packet won't leave by a bridge device or it is yet unknown what the output device will be, then the packet won't match this option, unless

--physdev-is-in

Matches if the packet has entered through a bridge interface.

--physdev-is-out

Matches if the packet will leave through a bridge interface.

--physdev-is-bridged

Matches if the packet is being bridged and therefore is not being routed. This is only useful in the FORWARD and POSTROUTING chains.

This modules matches the policy used by IPsec for handling a packet.

--dir in|out

Used to select whether to match the policy used for decapsulation or the policy that will be used for encapsulation. in is valid in the PREROUTING, INPUT and FORWARD chains, out is valid in the POSTROUTING, OUTPUT and FORWARD chains.

--pol none|ipsec

Matches if the packet is subject to IPsec processing.

--strict

Selects whether to match the exact policy or match if any rule of the policy matches the given policy.

--reqid id

Matches the reqid of the policy rule. The reqid can be specified with setkey(8) using unique:id as level.

--spi spi

Matches the SPI of the SA.

--proto ah|esp|ipcomp

Matches the encapsulation protocol.

--mode tunnel|transport

Matches the encapsulation mode.

--tunnel-src addr[/masklen]

Matches the source address of a tunnel. Only valid with --mode tunnel.

--tunnel-dst addr[/masklen]

Matches the destination address of a tunnel. Only valid with --mode tunnel.

--next

Start the next element in the policy specification. Can only be used with --strict

This module randomly matches a certain percentage of all packets.

--average percent

Matches the given percentage. If omitted, a probability of 50% is set.

Match on IPv6 routing header

--rt-type [!]type

Match the type (numeric).

--rt-segsleft[!]num[:num]

Match the `segments left' field (range).

--rt-len[!]length

Match the length of this header

--rt-0-res

Match the reserved field, too (type=0)

"--rt-0-addrsADDR[,ADDR...]

Match type=0 addresses (list).

--rt-0-not-strict

List of type=0 addresses is not a strict list.

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 RST 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.

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 --destination-port option of the TCP extension for details.

This is used to modify the IPv6 HOPLIMIT header field. The HOPLIMIT field is similar to what is known as TTL value in IPv4. Setting or incrementing the HOPLIMIT field can potentially be very dangerous, so it should be avoided at any cost.

Don't ever set or increment the value on packets that leave your local network!

mangle table.

--hl-set value

Set the HOPLIMIT value to `value'.

--hl-dec value

Decrement the HOPLIMIT value `value' times.

--hl-inc value

Increment the HOPLIMIT value `value' times.

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.

--log-uid

Log the userid of the process which generated the packet.

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

--set-mark mark

This target is an extension of the QUEUE target. As opposed to QUEUE, it allows you to put a packet into any specific queue, identified by its 16-bit queue number.

It can only be used with Kernel versions 2.6.14 or later, since it requires

the nfnetlink_queue kernel support.

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-prohibited
 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 protocol: 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).

This is used to explicitly override the core network stack's routing decision. mangle table.

--oif ifname

Route the packet through `ifname' network interface

--gw IPv6_address

Route the packet via this gateway

--continue

Behave like a non-terminating target and continue traversing the rules. Not valid in combination with `--tee'

--tee

Make a copy of the packet, and route that copy to the given destination. For the original, uncopied packet, behave like a non-terminating target and continue traversing the rules. Not valid in combination with `--continue'

This target has no options. It just turns on packet tracing for all packets that match this rule.

This target provides userspace logging of matching packets. When this target is set for a rule, the Linux kernel will multicast this packet through a netlink socket. One or more userspace processes may then subscribe to various multicast groups and receive the packets. Like LOG, this is a "non-terminating target", i.e. rule traversal continues at the next rule.

--ulog-nlgroup nlgroup

This specifies the netlink group (1-32) to which the packet is sent. Default value is 1.

--ulog-prefix prefix

Prefix log messages with the specified prefix; up to 32 characters long, and useful for distinguishing messages in the logs.

--ulog-cprange size

Number of bytes to be copied to userspace. A value of 0 always copies the entire packet, regardless of its size. Default is 0.

--ulog-qthreshold size

Number of packet to queue inside kernel. Setting this value to, e.g. 10 accumulates ten packets inside the kernel and transmits them as one netlink multipart message to userspace. Default is 1 (for backwards compatibility).