OS as your Router

Routers help you control network traffic by routing select traffic between different network segments using the best possible path. You can buy an expensive hardware router, or use your existing Windows NT/2000 or NetWare server installations to create software routers. Router usage depends on the network size. In our case, we created two network segments, A and B, and routed traffic between them using RIP (Routing Information Protocol). You’ll need to add a separate network card for each network segment and assign it a static IP address.

Windows 2000 Server Router



The routing service in Windows 2000 Server has some additional features like IP filtering. To configure it, do the following.

• Open Start>Programs>Administrative tools>Routing and remote access. On a management console that comes up, click on Action and select Configure and enable routing and remote access. A wizard lets you configure it as remote access server or Internet connection server. Choose network router and click next.

• Select the protocol you want. Since we chose to do IP routing, we selected TCP/IP.

• It asks you if you want to set up demand-dial connections. We chose no, as we only did routing on the LAN.

• Once the wizard is through, click on the plus sign against your network-server name, and then on the plus sign against IP routing.

• Right-click on the General tab, and select New Routing protocol. You can choose from various protocols. We chose RIP version 2, as we were routing only between two segments.

• Once RIP is added, right-click its icon, and choose New Interface. The next window shows all the network interfaces on your computer. Add these one by one. When you add one, it displays a window where you can configure the RIP properties for the interface. We left this to default settings.

• Your router is now ready for action. It will look for other routers on the network and update its routing table.

Windows NT Server 4.0 Router



Barring a few, the steps for this are similar to those for Windows 2000 server. For one, the Routing and Remote Access service isn’t a part of the OS, so you’ll have to download it from Microsoft’s website. If you received a Service Pack 3 CD from Microsoft, you’ll also find it there. Installation instructions for both are different, and in this case, we’ll focus on the 6 MB EXE file that can be downloaded. When it’s run, you’ll get a wizard similar to the one in Windows 2000. Choose the LAN-routing component. Your machine will be restarted, after which, go to Start Menu>AdministrativeTools> Routing and RAS Admin. The remaining steps are the same as for Windows 2000.

Router on Novell NetWare 5.1



Come to the System Console by pressing Ctrl+Esc, and selecting the option.

Run Inetcfg utility, and select ‘Bindings’. Press , select TCP/IP enabled and press enter. Select a network interface and specify a static IP address with subnet mask for each interface.

From the Inetcfg window, select ‘protocol’, then TCP/IP. Enable IP Forwarding and RIP by pressing enter on each option. You’ll get another window from where you can select enable or disable. Press Esc to save the configuration and exit.

Select Reinitialize system and your system will start routing.

Configuring the clients



At the client end, you need to configure their TCP/IP gateways. Go to the client’s Control Panel, choose network, and TCP/IP properties. Define the gateway IP address as the IP address of the routing server on the client’s segment. For instance, if it’s on the 192.168.1.x segment, then give 192.168.1.1 (or whatever IP address you’ve assigned to your routing server), which we defined above as the gateway. Do the same for the other segment. To test the connectivity, ping from a client on one segment to a client on the other. If you get a reply, then the router is working. Depending upon the size of your network, you may need more than one router. But make sure that all routers run the same routing protocol, else they’ll not be able to route.

Linux as a Router



Setting up dynamic routing in Linux using RIP is straightforward. First, make sure that you have IP forwarding enabled on the Linux machine acting as the router. For this issue the following command.

echo “1” > /proc/sys/net/ipv4/ip_forward

On the same Linux machine, install the RPM named routed-0.17-6.i386.rpm found on CD2 of PCQLinux 7.1 (July 2001 issue) in the directory RedHat/RPMS. Start the routing daemon named ‘routed’ as:

/etc/rc.d/init.d/routed start

To start the daemon automatically at subsequent reboots, issue ‘ntsysv’ on the Linux console and from the list of services select ‘routed’. The daemon automatically adds routing paths advertised by the routers on the network. You can peek into the dynamically constructed routing table using the command:

route —n

For further information and customized requirements see the man pages of the routed daemon as:

man routed