


The 'IP-Masquerading' feature ( IP-M ):

    In IP packages the IP-masquerading function manipulates
    for each outgoing IP package the sender's IP address and port.
    These manipulations are reset when incoming IP packages are received.


    When is IP-M useful?

    1.) Your provider has assigned you ONE dynamic or fixed IP address
        but you wish to provide other computers in your LAN with an
        internet access, too.

                                LAN

                                        10.1.1.1   +-----------+
                                    |              |  Linux    |
            +---------------+       +--------------+           |
            |               |       |              |           |
            |         10.1.1.254    |              +-----------+
            |               |       |
  ISDN      |  OS/2 mit     +-------+              +------------+
            |   ISDNPM      |       |   10.1.1.2   |  W95       |
  ......... |               |       +--------------+            |
            +---------------+       |              |            |
                                    |              +------------+
   132.130.4.5                      |
                                    |              +------------+
                                    |   10.1.1.3   |  OS/2      |
                                    +--------------+            |
                                    |              |            |
                                    |    ......    +------------+
                                    |

        The following configurations are required on your ISDNPM machine:

        1.1 Configuration of the Lan interface (TCPCFG.EXE)

        1.2 Make sure the forwarding of IP packages between your LAN
            and the serial interface (sl0) as well as the 'IP FORWARDING'
            function are active. (TCPCFG.EXE)

        1.3 The IP-M function must have been activated in 'isdn.cfg'

                [ip]

                ...

                if_masquerade : 2           // all IP packages will be
                                            // modified

                if_masquerade : 3           // the IP packages of the
                                            // computer on which ISDNPM is run
                                            // are not modified.
                                            // There may be Servers on this
                                            // computer.

        The 'DEFAULT-ROUTE' parameter of the computers making up the LAN
        must indicate to the OS/2 computer (10.1.1.254)


        1.4 If the IP address of your provider is assigned during a
            login procedure this must be made clear to the system.

             rc = SETLOCALIP(Channel,LocalIp)


    2.) Your provider has assigned you ONE dynamic IP address. This may
        cause problems when the connection is set up with 'AUTODIAL'
        (i.e. the IP connection is not achieved immediately)
        IP-M helps you to get around this problem.

        2.1 When configuring you ISDNPM pretend to have a fixed IP address
            (NO 'IfconfigFile' in isdnuser.cfg and NO interface configuration
            in TONLINE.FNC)

        2.2 Activate IP-M in 'isdn.cfg'

                [ip]

                ...

                if_masquerade : 2           // all IP packages will be
                                            // modified

    What IP-M cannot do:

    It is NOT possible to establish any connections to the PCs of the LAN
    from outside (from the internet).
    When ISDNPM is installed on a PC this machine may NOT be used as a
    server (for FTPD...).

