ok. so, i have asked the network admin whether he created vlans on the switch for each subnet with regards to the previous NAT server. Actually, he didn't. He just created the 2 subnets from the NAT server, which is Windows 2000, trunked to one interface and didn't do anything with the switch. On the Windows server, he first entered an IP which is 192.168.2.1/23 and added another IP for the same interface which is 192.168.3.1/24. The result are two subnets that can route data to each other. I wish I could do the same with pfSense. Thanks