If You've Got It, Use It

A little creativity can go a long way

Many times, IT personnel need to find creative workarounds for equipment needs that aren't in the budget or for which no commercial solution exists. When you find yourself in this situation, look around and consider whether you can use existing tools to solve the problem. For example, the Lab Guys recently needed a 10-port static router for the Lab's benchmark-network upgrade, but the cost of a commercially available product was a problem. Building a multihomed system and configuring it for IP forwarding seemed like a simple and cost-effective solution.

We had to find a way to place 10 network ports on one system. First, we gathered two 4-port NICs and one 2-port NIC. Because meager computing power doesn't hamper a static router, we chose to configure an unspectacularly equipped, custom-built Celeron system that had no unnecessary IRQ-consuming peripherals.

Although we could have used Windows NT Server, we implemented the router on a Windows 2000 server to become more familiar with Win2K's routing abilities. This choice led to some interesting discoveries and taught us that creative workarounds require creative problem-solving throughout the process. First, we determined that the previous-generation Adaptec 4-port NIC cards we planned to use weren't Win2K-compatible. After a quick Web search and a call to Adaptec, we decided to install two Adaptec Quartet64 ANA-62044 4-port, 64-bit PCI NICs. After we acquired the proper hardware, Win2K automatically detected those NICs and our Adaptec Duo64 ANA-62022 2-port, 64-bit PCI NIC during Win2K installation and uneventfully installed the drivers that came with the NICs. We assigned each port an appropriate IP address for the network segment to which the port would attach.

Then, we made the second interesting discovery: The Enable IP Routing check box, which NT's Advanced Microsoft TCP/IP Configuration dialog box contains, doesn't exist in Win2K. (For more information about the differences in enabling IP routing in Win2K and NT, see David Chernicoff, Forefront, "Working with Windows 2000," June 2000.) We finally found an explanation in Chapter 3 of the Windows 2000 Server Resource Kit: By default, Win2K disables IP routing.

According to the resource kit, to enable IP routing, you must change the Win2K system Registry. When you enable RRAS for IP routing, Win2K automatically creates the IPEnableRouter Registry entry under the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters key. To enable IP routing for all installed network connections, you must assign a value of 1 to this entry. When we enabled RRAS, static routing worked, but Win2K didn't change the Registry. When we disabled RRAS, IP routing ceased. Then, when we manually changed the Registry and rebooted, routing worked. A Microsoft representative confirmed that the resource kit information isn't up-to-date and explained that when you enable RRAS in the Routing and Remote Access Microsoft Management Console (MMC) snap-in, the router manager makes an I/O control call to the TCP/IP stack to enable IP forwarding. (Microsoft believes that the MMC procedure reduces the risk of human error and is much safer than editing the Registry.) We configured and tested our internal routes; they all worked.

As a bonus to our creative solution, we had a chance to play with Win2K's useful Pathping command. Pathping is a new route-tracing tool that combines the features of Ping and Tracert. To help you pinpoint problem routers or links, Pathping monitors packets that routers return from each route hop, then computes a degree of packet loss for each hop.

Our 10-port Win2K router cost $16,000 less than a commercial router chassis with the same number of ports. Sometimes a solution to a difficult problem requires only a little creative thinking and knowledge about your existing tools' capabilities.