If you have the DBC2C20 board than their homepage states: "Several Ethernet based reference designs, a NIOSII getting started tutorial, and a standard reference designs are delivered with the board."
If you would like to conect a LAN91C111 chip to your custom board than:
- check the schematic and Quartus project for one of the Altera Nios II Development Kits (the one that uses the same Altera chip)
- check Quartus II projects for the board for example the Full Featured
The schematic and projects can be found in your Quartus and Nios installation directory under:
C:\altera\kits\nios2_60\documents C:\altera\kits\nios2_60\examples\vhdl IzI