If you change a ip address you must download this information to the hardware file otherwise when the power is cycled the CPU will revert to the old address. You need to write to the flash memory too. One great Proficy ME feature is using the set ip address to first communicate to a CPU on the LAN. I document the MAC address for each CPU which is needed for this software function to work. For remote communications I use product from PLCRemote.net. Great product that really works. I have communicated with sites in China and India from our offices in Northern Nevada replacing old dialup modems.