administration tool for IPv4 packet filtering and NAT

-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.

[!] -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).

-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.