ACTIVE DIRECTORY 2003

Hi need your help

I have a 2 segments 192.128.1.1/24 and 192.128.1.2/24 which both connected to the firewall. My domain controller is connected to 192.128.1.1/24 and my pc which i will join to the domain is connected to 192.128.1.2/24. my problem is i cannot join the pc to the domain eventhough i can ping the IP of the domain controller.