Internet and local network through the same network card???

[alejdesa]

Hi, I'm having some troubles trying to connect to the internet at the same time I try to access my internal network. To connect to the internet, I have a cable modem wich connects to each PC through a switch. I have 3 DHCP IP (one for each computer) that are assigned by mi ISP. My problem is that I also want to connect to my local area network. To do that I've installed a new network card on each PC and connected them to the switch. Then I configured one card to obtain an automatic IP (DHCP) and the other card manually to obtain xxx.xxx.x.1, etc...
The problem seems to be that when the PCs starts up, the switch assigns a dynamic IP to the card that shouldn't have. So many times I get that one of the PCs have a DHCP IP 169.xxx.x.x wich means that it is internal when it should be a remote address (to connect to the internet). So someone at the internet company told me that I could use the same network card to connect to the internet and to the local area network; but he didn't want to tell me because he said the company doesn't allow him to do so. Is it possible??? What protocol should I use instead of TCP/IP???

Please, help me with this, fellows!!

Thanks and hope your answers.

Alejandro.-

[johnwill]

I'm curious as to why you don't just use a router. Depending on the ISP to assign your IP addresses in the same subnet is pretty risky. In addition, you're also opening up your file shares to the public connection, another bad idea.

I suggest you buy a broadband router and connect all the computers to the router. You'll have shared Internet access, a hardware firewall protecting all the systems, and they'll all be in the same subnet for file/print sharing.