By having the software insert the 16-bits “FF-FF” or “FF-FE” in between the OUI and EI, the EUI-48™ address can be converted to a unique EUI-64™ node address. These 16-bit codes have been specifically reserved by the IEEE to help convert an EUI-48 node address to a unique 64-bit MAC address. So in the example shown here, the 48-bit node address is 00-04-A3-12-34-56 while the corresponding 64-bit node address is 00-04-A3-FF-FE-12-34-56. The IEEE also issues individual OUIs for EUI-64 blocks but they ensure that they don’t use the 2 bytes above.