RSLinx Classic Gateway essentially allows you to use local RSLinx drivers remotely over a TCP network. Often these are drivers that use specific hardware resources (DF1, DH+, ControlNet) but they don't have to be.
There are three things you need to do to configure and use RSLinx Classic Gateway:
1. The client computers need to be on the same IP network as the RSLinx Classic Gateway computer. Make sure you can "PING" the Gateway computer.
2. Enable the RSLinx Gateway function on the Gateway computer. From the RSLinx Classic menu, choose Communications -> Configure Gateway, and check the "Enable RSLinx Gateway" function.
3. Configure the "Remote Devices via RSLinx Gateway" driver in RSLinx Classic on the client computers. This will let you choose the Gateway computer, and select the driver you're going to access remotely. These computers can have any license of RSLinx Classic, including Lite.
Do these three things and post details if any of them don't work for you.