administration tool for IPv4 packet filtering and NAT
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-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.
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[!] -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 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 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).
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[!] -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, esp, ah, sctp 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.
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[!] --destination-port,--dport port[:port]
Destination port or port range specification. The flag --dport is a convenient alias for this
option.
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-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.
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