Brother NC6100H - Manual (Page 133)

A - 6 APPENDIX
If you encounter problems upgrading the firmware and you
find that the network portion of the printer no longer functions,
you should try re-programming the print server by using the
COPY command from the DOS prompt of your PC. To do
this, connect a parallel cable between your PC and printer
and use the command
COPY filename LPT1:/B (where
filename is the new firmware file).