OK, but from what Be Be says he uses Cypress EZ-USB FX2. I am using the same uC for my final year's project and as far as I know this 8051 derivative does not have on-chip flash memory, so Be Be needs to use some kind of ROM memory. Of course it is true that you can't implement the ethernet data packet storage in ROM ;)

Also FX2 has 8K of on-chip RAM. I don't know anything about TCP/IP implementation (only some theory about it), but isn't the on-chip RAM of the FX2 uC enough for such a project?

Also I wonder: Be Be you say that your project is about designing a LAN card and for that project you have selected Cypress EZ-USB FX2. Why didn't you pick an 8051 derivative with integrated networking capabilities, such as the DS80C400 from Dallas? Or you want to implement a LAN card using the USB bus?