Provided by: firehol-doc_3.1.7+ds-2_all bug


       firehol-masquerade - set up masquerading (NAT) on an interface


       masquerade real-interface rule-params

       masquerade [reverse] rule-params


       The  masquerade  helper  command  sets  up  masquerading  on  the output of a real network
       interface (as opposed to a FireHOL interface definition).

       If a real-interface is specified the command should be used before any interface or router
       definitions.   Multiple  values  can be given separated by whitespace, so long as they are
       enclosed in quotes.

       If used within an interface definition the definition’s real-interface will be used.

       If used within a router definition the definition’s outface(s) will be used, if specified.
       If  the  reverse  option  is  given,  then  the  definition’s  inface(s)  will be used, if

       Unlike most commands, masquerade does not inherit its parent definition’s rule-params,  it
       only  honours  its own.  The inface and outface parameters should not be used (iptables(8)
       does not support inface in the POSTROUTING  chain  and  outface  will  be  overwritten  by
       FireHOL using the rules above).


              The masquerade always applies to the output of the chosen network interfaces.

              FIREHOL_NAT  will  be  turned  on automatically (see firehol-defaults.conf(5) ) and
              FireHOL will enable packet-forwarding in the kernel.


       Masquerading is a special form of Source NAT (SNAT) that changes the  source  of  requests
       when  they  go out and replaces their original source when they come in.  This way a Linux
       host can become an Internet router for a LAN of clients having  unroutable  IP  addresses.
       Masquerading takes care to re-map IP addresses and ports as required.

       Masquerading is expensive compare to SNAT because it checks the IP address of the outgoing
       interface every time for every packet.  If your host has a static IP  address  you  should
       generally prefer SNAT.


               # Before any interface or router
               masquerade eth0 src dst not

               # In an interface definition to masquerade the output of its real-interface

               # In a router definition to masquerade the output of its outface

               # In a router definition to masquerade the output of its inface
               masquerade reverse


firehol(1) - FireHOL program

       • firehol.conf(5) - FireHOL configuration

       • firehol-interface(5) - interface definition

       • firehol-router(5) - router definition

       • firehol-params(5) - optional rule parameters

       • firehol-nat(5) - nat, snat, dnat, redirect config helpers

       • FireHOL Website (

       • FireHOL Online PDF Manual (

       • FireHOL Online Documentation (


       FireHOL Team.