Hi, I am not a hardcore programmer . I have only basic knowledge of programming. I have a PLC project created in TIA Portal v15. In this project, 8 units of SEW Eurodrive are configured and connected to the PLC through the SEW Profinet I/O gateway (DFE 32B/UH11B). Recently, this Profinet I/O gateway got damaged. We don't have a spare with us , so we decided to go with another refurbished one. When we connected the first refurbished unit, the Run LED was green, and the H1 LED was red, but in the HMI, all the connected drives were in an error state. We then replaced this gateway unit with another refurbished one; this time, the Run LED was green along with a bus fault. This time, a Profinet I/O device not found error was shown in the CPU display , and the VFDs remained in an error state. After this issue, the supplier of the refurbished unit did come to copy data between these two refurbished units . Then we connected the gateway, and it worked perfectly, with the VFDs showing the correct status in the HMI. The machine started running normally. However, during all this time of replacement and until now, the MAC address of the SEW gateway in the CPU display hasn 't changed ; it still shows the damaged device's MAC address. 

So my questions are:

1. How can we update this MAC address ? 

2. Is it necessary to update the MAC address ?

3. What is the reason for the MAC address not changing ?