At the very least you'll still need some magnetics. ;-) I would guessthat you'd also need a PHY, but I am not sure... I would expect the ethernet MAC + some fifo's to be implemented inside the fpga, and then PHY etc outside. But as said, at the very least you need the magnetics so you will always need some external hardware.
What it means is you can use logic inside the FPGA fabric rather than using a dedicated hard core to do it. Using a hard coure uses no internal resources other than the hard core itself, maybe a little for routing. Hard cores can usually be clocked faster.
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and no external interface is needed for either option.
so wat i understood is that i will need to design a core inside the FPGA no external IC is required. Only the Connector is to be connected at the output of the FPGA