Ethernet IESM and EEPROM

I did not find any technical (hardware architecture,…) about the Ethernet IESM and the sample code is poorly commented.

Can somebody explain me the role of the M24CXX (16?) EEPROM regarding the Microchip ENC28J60 Ethernet ?
I understood that the MAC Address is available at the address 0 of the EEPROM… right ? Does the microchip write it there everytime it is initialized ?

And finally to initialize the Ethernet IESM, if I know the MAC address, do I really need to read this value and do I really need the I2C_E2P_M24CXX interface (extstorage_iic.c) or can I remove it ?

thanks !