Brother MFC 5840CN - Manual (Page 33)

3 - 12 FRONT PANEL SETUP
NC9100h_FM6.0
Restoring the Network Settings to Factory Default
To restore all network settings of the internal Print/Scan server to
factory default, please follow the steps below.
1 Make sure the machine is not operating, then disconnect all the
cables from the machine (except power cable).
2 Press Menu/Set , 5 , 0 . ( 4 , 0 for MFC-5440CN)
3 Press 1 to select Reset.
4 Press 1 to select Yes.
5 The machine will re-start, re-connect cables once this is
complete.