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4. Configuring the VPN client

4.1 Configuring a MS W'95 or W'98 client

  1. Set up your routing so that the Linux firewall is your default gateway:
    1. Open Control Panel/Network or right-click "Network Neighborhood" and click on Properties.
    2. Click on the Configuration tab.
    3. In the list of installed network components, double-click on the "TCP/IP -> whatever-NIC-you-have" line.
    4. Click on the Gateway tab.
    5. Enter the local-network IP address of your Linux firewall. Delete any other gateways.
    6. Click on the "OK" button.
  2. Test masquerading. For example, run "telnet my.isp.mail.server smtp" and you should see the mail server's welcome banner.
  3. Install and configure the VPN software. For IPsec software follow the manufacturer's instructions. For MS PPTP:
    1. Open Control Panel/Network or right-click "Network Neighborhood" and click on Properties.
    2. Click on the Configuration tab.
    3. Click on the "Add" button, then double-click on the "Adapter" line.
    4. Select "Microsoft" as the manufacturer and add the "Virtual Private Networking Adapter" adapter.
    5. Reboot when prompted to.
    6. If you need to use strong (128-bit) encryption, download the strong encryption DUN update from the MS secure site at http://mssecure.www.conxion.com/cgi-bin/ntitar.pl and install it, then reboot again when prompted to.
    7. Create a new dial-up phonebook entry for your PPTP server.
    8. Select the VPN adapter as the device to use, and enter the PPTP server's internet IP address as the telephone number.
    9. Select the Server Types tab, and check the compression and encryption checkboxes.
    10. Click on the "TCP/IP Settings" button.
    11. Set the dynamic/static IP address information for your client as instructed to by your PPTP server's administrator.
    12. If you wish to have access to your local network while the PPTP connection is up, uncheck the "Use default gateway on remote network" checkbox.
    13. Reboot a few more times, just from habit... :)

4.2 Configuring a MS NT client

Note: this section may be incomplete as it's been a while since I've installed PPTP on an NT system.

  1. Set up your routing so that the Linux firewall is your default gateway:
    1. Open Control Panel/Network or right-click "Network Neighborhood" and click on Properties.
    2. Click on the Protocols tab and double-click on the "TCP/IP" line.
    3. Enter the local-network IP address of your Linux firewall in the "Default Gateway" box.
    4. Click on the "OK" button.
  2. Test masquerading. For example, run "telnet my.isp.mail.server smtp" and you should see the mail server's welcome banner.
  3. Install and configure the VPN software. For IPsec software follow the manufacturer's instructions. For MS PPTP:
    1. Open Control Panel/Network or right-click "Network Neighborhood" and click on Properties.
    2. Click on the Protocols tab.
    3. Click on the "Add" button, then double-click on the "Point-to-Point Tunneling Protocol" line.
    4. When it asks for the number of Virtual Private Networks, enter the number of PPTP servers you could possibly be communicating with.
    5. Reboot when prompted to.
    6. If you need to use strong (128-bit) encryption, download the strong encryption PPTP update from the MS secure site at http://mssecure.www.conxion.com/cgi-bin/ntitar.pl and install it, then reboot again when prompted to.
    7. Create a new dial-up phonebook entry for your PPTP server.
    8. Select the VPN adapter as the device to use, and enter the PPTP server's internet IP address as the telephone number.
    9. Select the Server Types tab, and check the compression and encryption checkboxes.
    10. Click on the "TCP/IP Settings" button.
    11. Set the dynamic/static IP address information for your client as instructed to by your PPTP server's administrator.
    12. If you wish to have access to your local network while the PPTP connection is up, see MS Knowledge Base article Q143168 for a registry fix. (Sigh.)
    13. Make sure you reapply the most recent Service Pack, to ensure that your RAS and PPTP libraries are up-to-date for security and performance enhancements.

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