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Advanced Networking for Mactintosh Professionals


User Guide


PPPoE Internet Sharing with IPNetRouter

  1. Choosing the Proper Setup Method for PPPoE Sharing
  2. PPPoE Dual Ethernet Internet Sharing
  3. LAN Client Configuration for PPPoE
  4. Other Configuration Notes For PPPoE LANs

Choosing the Proper Setup Method for PPPoE Sharing

There are now two classes of PPPoE ("PPP-over-Ethernet") connection software on Macs – those that use Remote Access (RA) and those that do not. The instructions in this chapter were originally written assuming you had an older style PPPoE drivers that did not use Remote Access. Older style PPPoE connection software include EnterNet (non-RA version), Sympatico, AccessManager, or MacPoet. If your DSL Internet connection instead requires Remote Access (eg Enternet RA or Alcatel USB modem) for high speed access, read the next few paragraphs and then follow the directions in the "Internet Sharing using Remote Access and Ethernet" chapter. MacDSL, T-DSL , and EnterNet (RA version) use Remote Access for PPPoE connectivity.

We strongly recommend that you download and install IPNetRouter 1.5 or later for use with PPPoE Internet sharing. If you must use an older version of IPNetRouter, LAN client configuration will be more complicated.

If you have a single ethernet configuration then you might not want to use MacPoet. You can download the EnterNet client software and try that if you have problems configuring MacPoet. Read all instructions thoroughly before beginning an installation.

Although many users have dual ethernet configurations working on nubus Macs with PPPoE drivers, we have few reports of single ethernet (one port) nubus Mac sharing their connection. If you manage to get such a configuration to work, please let us know!

PPPoE Dual Ethernet Diagram

PPPoE Dual Ethernet Internet Sharing

Basic steps to configure IPNetRouter with PPPoE or LANTunnelBuilder 5.0.9a in a dual ethernet setup:

  1. On the gateway machine, use the TCP/IP control panel to configure the PPPOE driver for the DSL/ADSL modem as instructed by your service provider. Make SURE that the "Load Only When Needed" option is UNCHECKED. (You must be in Advanced User mode to get to the TCP/IP options. Choose User Mode under the Edit menu and select Advanced.) If you can already access the Internet from this machine via your DSL/ADSL modem and you are SURE that the "Load Only When Needed" option is UNCHECKED in the TCP/IP control panel, you're ready to proceed to the next step.
    IF you are using an older NuBus machine to run IPNetRouter, this DSL/ADSL modem connection MUST be made into the built-in ethernet port. With PCI bus machines, the cable/DSL/ADSL modem can be plugged into either ethernet port.
  2. Open your PPPoE client and connect to the internet before launching IPNetRouter. The PPPoE driver must be loaded with an active connection before IPNetRouter is running. Verify that you can connect to the internet with a browser and then quit the browser. If you do not do this first, you may experience problems configuring IPNetRouter, including crashing and hanging of your system.
  3. After connection with the PPPoE client, launch the IPNetRouter application. Verify that you can still connect to the internet with a browser and quit the browser before proceeding to the next step.
  4. In the Interfaces window, click on the top row (with your public IP address on the ethernet port). With this interface selected, check the "IP masquerading" box, check the the "DHCP Aware" box, and click Add. You should see a little mask icon appear in the state column for the PPPOE interface and a DHCP icon. Notice you need to enable IP Masquerading on the interface that communicates directly with your DSL/ADSL modem through the PPPOE driver. Your Interfaces window should now appear similar to the following (your Port Name, IP address and mask values will vary depending upon the PPPOE driver you use and the IP and mask values assigned by your ISP):

  5. In IPNetRouter's Gateway window, make sure that IPForwarding is "Automatic", and that the following are checked:
    • "Remain Connected"--if the PPPoE connection times out while IPNetRouter is running, your system may hang if you try to reconnect.
    • "Better PPPoE Routing" (versions 1.5c12, c14 and later) or "Limit MTU for PPPoE" (1.5c8-11)

  6. Next you need to create a 2nd IP interface on your other Ethernet port. Continue to work in the Interfaces window using the "Configure Interface" input area just below the main display grid. Select the other ethernet port from the popup menu under the Port Name column. The corresponding interface name is entered for you automatically (you should not need to change this). Enter a local IP Address and Mask. We suggest and respectively. Only the "Bring Up" checkbox should be checked. Press Add. You should see all the values you just entered appear in a new row in the main Interfaces table.

  7. Select SaveAs from the File menu to name and save your configuration. Launch the PPPoE client and then double click on this config file anytime you want to startup IPNetRouter with this configuration. Your gateway should now be working! If it doesn't work right away, try restarting once to give Open Transport a chance to rebuild your TCP/IP stack with the supplied Proxy module inserted.
  8. See Slave Configuration below.


Single Ethernet Configuration for PPPoE

For the PPPoE Single Ethernet configuration you will be following many of the steps used in the dual ethernet example above. This example works with LanTunnelBuilder (LTB), EnterNet 1.09 and Sympatico/Access Manager, both derivatives of the LTB software. The following is for an iMac running OS 9 but should work on any PCI Mac and some nubus configurations:

  1. Read the introduction to PPPoE configuration. Carefully follow steps 1-5 for dual ethernet PPPoE configuration.

  2. Verify that you can connect to internet with a browser and quit the browser.

  3. To configure your LAN interface, create a second interface (EnterNet) should appear by itself initially) in the Interface window using the Ethernet built-in interface as shown in the diagram...

  4. Follow steps 7-8 for dual ethernet PPPoE configuration.


LAN Client ("Slave") Configuration With PPPoE

Now each slave machine on your LAN needs to be configured to take advantage of this new gateway:

  1. Each slave machine needs its own unique IP address from the same private sequence that the gateway is using. In the above example the gateway is at, so your slaves should each use a unique addresses like, or 192.168.0.X where X is anything from 2 up to 255.

  2. All the slave machines need to be told to use the gateway machine ( to access the Internet. So set the Default Gateway (router) parameter of all slaves to

  3. You can use the IPNetRouter IP address as the Name Server address in each of the clients (e.g. Just make sure that the DNS forwarding option is checked in the Gateway window of IPNetRouter. (you MUST be running IPNetRouter v1.4.8 or later for DNS forwarding). Otherwise you need to enter the true Name Server for your ISP in each of the client machines.

  4. With the dual ethernet setup only, you can use the DHCP server within IPNetRouter to configure your client machines. This may be easier than individually and manually addressing each of the client machines on your private network. Using the DHCP server within IPNetRouter is quite simple: just open the DHCP window and click the DHCP Server On checkbox and click Done. There are, however, many other options you can configure with the DHCP server. Please see the Help window in the DHCP window for more information. You should never enable IPNetRouter's DHCP server feature in a single ethernet configuration with a cable/xDSL modem--there is a limitation in the DHCP standard that prevents this from working correctly.

  5. When using IPNetRouter prior to 1.5, you must install IPNetTuner to set the Maximum Transmission Unit (MTU) on each of your Mac client machines. Set the MTU size to somewhere between 1350 and 1482 bytes on each Mac. Regedit can be used to set the MTU on Windows clients. Skip having to do client configuration for MTU by checking the "Better PPPoE Routing" checkbox in the Gateway options window of IPNetRouter 1.5 or later. "Better PPPoE Routing" negotiates the MTU with your clients automatically.


Other Configuration Notes For PPPoE LANs

Email and Browser applications running on the client machines should have their servers (such as mail and news servers) set to the standard values specified by your provider. You may, however, have to use FULLY SPECIFIED DOMAIN NAMES for Mail servers when accessed from your client machines (e.g. instead of just using "mail" for the SMTP mail server, you might have to fully specify the name like ""). Also make sure the slaves each have a unique IP address and will use the gateway (typically as their default gateway. On a Mac use the TCP/IP or MacTCP Control Panel, on Windows use the Network Control Panel.

If you need to determine the IP address of the default Name Server (DNS) which your ISP has you currently using, you can use the IPNetRouter log window, the PPPoE client info window, or the tools in IPNetMonitor to determine this IP address. From the gateway machine, launch IPNetMonitor and open the NSLookup Window (Name Server Lookup). From the NSLookup window, open the Ping window (Cmd-T), this will invoke a ping test to your default Name Server, used by NSLookup. Your default Name Server address will be visible in the Ping window. You could then use this IP address in each of your client machines... but just using your gateway's local LAN address with DNS forwarding is normally much easier.

IP Addressing: I chose the example IP addresses from network 192.168.x.x because this network range is reserved for private Internets (see RFC 1918). In order to route IP datagrams between two networks, each network must normally have its own network number (the most significant part of the IP address logically ANDed with the network mask). If you wish to follow the suggested example, each machine on your ethernet LAN must have a unique address from network 192.168.0.x (,,, etc.). The Macintosh running IPNetRouter ( in this example) becomes the default router or gateway for the other machines on your ethernet LAN. You can use a different network address in this range, 192.168.111.x or 192.168.3.x, for example, instead of 192.168.0.x.

See the Troubleshooting and OS 9 Compatibility section, Read Me and release notes documents included in your installation folder, and the FAQ page on our web site for more info on configuring your LAN with IPNetRouter.