The ThinkPad was updated with Service Pack 4 and the most recent security patches. It was connected to the Internet via a high-speed satellite system from Hughes networks. The satellite interfaced with the laptop through a USB port, creating its own virtual network adapter inside the Network and Dial-up Connections. The IP address, subnet mask, and a default gateway were hard-coded into the system, as were two specific DNS servers. The Internet Service Provider, the satellite company, provided these settings to the client. The laptop also had a built-in 100Mbps Ethernet network card. This adapter was not physically connected to anything. It was set to obtain its IP configuration information dynamically. It currently held an APIPA (Automatic Private IP Address) in the 169.254.x.x range, assigned by Windows 2000 Professional.

The Apple software was up-to-date with version 10.2.6 installed. I opened the network properties in System Preferences and set the internal network card on the Macintosh as the default and for it to obtain its IP configuration automatically. Its current settings also corresponded to APIPA.

Since these were the only two computers to be networked, we decided to connect the two using a CAT-5 Crossover cable. With the cable plugged in to both network cards, I noted blinking activity lights on the card inside the ThinkPad. I enabled the taskbar network activity icon, which appears at the lower right corner of the Windows 2000 Professional desktop, to demonstrate that the two machines were physically connected.

The next step was setting up ICS (Internet Connection Sharing) on the Windows 2000 Professional system. By enabling this feature, Windows 2000 provides dynamic IP addressing, NAT (Network Address Translation), and DNS (Domain Name resolution Services) for all computers networked to it. The function of NAT is to translate requests for Internet resources from internal machines, with internal IP addresses, to external networks through the host machine’s Internet connection. This is what allows the sharing of a single public IP address between all the machines on the internal network. The DNS service is what resolves the host name (i.e. an Internet name like www.microsoft.com) typed in a web browser to its corresponding IP address.

In the properties of the satellite network adapter, I clicked on the Sharing tab and checked the box to Enable Internet Connection Sharing for this Connection. I then clicked OK and exited to the desktop. An important thing to remember is that ICS settings cannot be changed. One cannot control the IP addresses that ICS distributes (in the 192.168.1.x range) nor change any addresses that ICS has already handed out.

I rebooted the Macintosh and checked the settings on the network card. It was receiving an internal address (192.168.1.x). This proved that the connection to Windows 2000 Professional was working, and ICS assigned itself as the default gateway on the Macintosh. However, when I tried to contact an Internet site, I was unable to obtain any information, regardless of typing a URL (i.e. www.microsoft.com) or an IP address.

I returned to check the settings on the ThinkPad. I dropped out to a command prompt and used the ipconfig /all command to check the TCP/IP settings on both the virtual and the built-in adapters. The built-in adapter had been configured by ICS to 192.168.1.1 with a Class C subnet mask (255.255.255.0) and no gateway. The virtual adapter had maintained its hard-coded IP address and subnet mask, but the entry for the gateway had been cleared. I realized connectivity to the Internet could not be made without a default gateway, so I manually entered the settings I had recorded before enabling ICS on the satellite’s virtual interface.

At this point, with the ThinkPad and the Macintosh able to connect to the Internet, I decided to establish file sharing between the two. To share files between Windows and OS X, enable File Sharing to create a common folder accessible on both computers.

On the Macintosh, I clicked on the Accounts icon inside System Preferences. I selected the client's home folder and clicked Edit User, checking Allow user to log in from Windows and then OK. Next, I clicked on the Sharing icon, checking Personal File Sharing and Windows File Sharing. I noted the Macintosh IP address at the bottom of the window, since this is the address required on the PC to establish the share point. On the Windows machine, I searched for the IP address of the Macintosh and accessed the shared folder by entering the username and password of the Macintosh user.

To share a folder from Windows, I created a new folder and clicked on the Sharing tab in the Properties of the folder. I enabled Share this folder on the network to allow the folder to be read by the Macintosh and then clicked on Allow network users to change my files to allow writing by the Macintosh. I then clicked Apply and OK. On the Macintosh, I opened the Finder, clicked Go, and traced down to Connect to Server. I entered the IP address of the PC I wanted and hit Connect. I entered the Macintosh username and password and clicked OK. Then I clicked on the name of the shared folder I wanted and clicked OK. This caused the folder to appear on the Macintosh desktop, allowing me to copy files from Windows or OS X to the folder and retrieve them on the other computer.

I now had a completely shared, multi-platform network installed.

Until next month…