Reference Manual

HOW TO configure NAT32 for PPPoE:

The PPPoE protocol is commonly used by DSL devices which connect to your machine via an Ethernet Adapter. It is very similar to the PPP protocol used with conventional modems, but one difference is that it can be used to communicate with any of several DSL devices which might be attached to an Ethernet network.

Note that if you are using NAT32 to share a private IP address assigned by a DHCP server running on a DSL Router, none of the following information applies, and you should configure that NAT32 Interface as a normal "Internet-connected" LAN interface.

If you are using NAT32 to share a USB DSL Modem, none of the following information applies either, and you should configure that NAT32 Interface as a normal "Internet-connected" Dial-Up Networking interface.
Before purchasing a USB DSL modem, be sure to read this page.

One problem with PPPoE is that there exist several different ways of supporting it under Windows. Most current PPPoE drivers use a Dial-Up Networking paradigm and require the user to establish a DUN Connection to an ISP via the DSL Modem. Several legacy PPPoE drivers requiring the installation of large, vendor-specific PPPoE applications are still being distributed by ISPs, and it is strongly recommended that you do not install such applications.

The best PPPoE driver by far for pre-Windows 7 systems is the free RASPPPOE driver. It runs on all Windows platforms and is the only driver of its kind known to handle MTU issues correctly and transparently.

The MTU problem arises because PPPoE requires 8 bytes of additional header information in each packet it transfers, thereby reducing the normal Ethernet MTU of 1500 bytes to 1492 bytes.

The RASPPPOE web site supplies full installation and configuration instructions.

To configure NAT32 for RASPPPOE, be sure to first establish the connection to your ISP and then select that Dial-Up Networking Connection in the NAT32 Interface Selection dialog box. In the subsequent Interface Configuration dialog box for that connection, be sure to check the DSL/PPPoE checkbox (if shown) and set the MTU to 1492 bytes.

Note that you do not need to select the actual Ethernet Adapter over which the PPPoE traffic is flowing, because that traffic is of no further interest to NAT32. Be sure you have given that Ethernet adapter a dummy IP address like 10.1.1.1 so that Windows TCP/IP does not try to configure it at boot time via DHCP.

HOW TO configure NAT32 for Legacy PPPoE Drivers:

Sympatico High Speed Edition Adapter (NTSPPP3)

To configure NAT32 PPPoE support for this adapter, procede as follows:

• Download the current build of NAT32.
• On Windows 9X platforms, add this line to your NAT32 startup file, anywhere before the last echo command:
seti p -1 1472
• On Windows NT4 platforms, add this line instead:
seti p -2 1472
• The seti command sets the NAT32 Primary interface to PPPoE mode and instructs NAT32 to use an MTU of 1472 bytes on that interface. Please experiment with that value, as some users have reported that 1412 bytes works best.

WinPoet

Some ISPs distribute a product called WinPoet, which also implements PPPoE within Windows Dial-Up Networking.

NAT32 configuration for WinPoet is very similar to RASPPPOE configuration, although you may find that an MTU of 1472 bytes or less is required.

SEE ALSO

conf, mtu, seti