You can set the CPU IP address, subnet mask and gateway via the CAT mode (programming through the display phone).
Go off line into the CAT mode by pressing; TRF + CNF + * + TRF + CNF + #. Press redial to get to "COMMAND = ". Press 0 + # + 0 + 0 + recall. Press 0 + 0 + recall to see the IP address. If you wish to change it, type in the new address via the keypad. Make sure you input all 12 octet digits including any lead 0's. Press CONF to write the data, press SPEAKER to advance to the SNM area. Type in the new SNM + CONF to write it. Press SPEAKER to advance to the gateway area. Type in the new gateway, then press CONF to write it. Press redial to go back to COMMAND = . You need to back this up to the flash ROM. Press line key 5 (= E) + line key 3 (= C) + 6 + RECALL. type in 0 + CONF to start the back up process. Wait at least 5 - 10 minutes to complete. Go back to CMD EC6 + recall to verify the back up is complete. A display of 3 = done, 1 = in progress. Next, to implement the new address you must reset the system. This will interrupt all call traffic for 90 to 120 seconds.