Hi  @Dinis124,

If you want multiple Range Extenders to extend Wi-Fi coverage, we recommend connecting all Range Extenders directly to the host Router.

Range Extenders can be daisy-chained (connect one extender to the other), but we do not recommend using more than 2 extenders in one daisy chain.

For more detailed configuration recommendations, please refer to https://community.tp-link.com/en/home/forum/topic/155927

For your problem, it seems that it is not directly related to the firmware version. If the device sends many ARP frames to the network at a rate of about 5 ARP frames per second, it may be due to many connected clients or frequent communication.

Please check if there are other devices connected to your network besides the client device you are using?

Please turn off all TL-WA850RE and confirm whether the problem still exists when the client device is connected to the router? If yes, the problem mainly comes from the router.

If the problem disappears, please use a separate TL-WA850RE and move the TL-WA850RE closer to the router to check if the same problem still exists? If yes, the TL-WA850RE may not be suitable for your environment. Range extender mainly extends the network through wireless means. It is recommended that you consider Access Point.

  @Joseph-TP 

I did not daisy-chain the repeaters, I connected both of them to the same switch via an ethernet cable.

I don't think it is due to connected clients because, as I mentioned, the ARP frames are coming with the TL-WA850RE on the "Tell" (who initiated the ARP request) field. If the frames were due to clients connected to the TL-WA850RE, they would contain the initiator's IP addr in the "Tell" field, not the TL-WA850RE's IP address. One of the TL-WA850RE even had 0 clients connected to its hosted wifi network. Also, Wireshark identified the source MAC Addr of the frame as a TP-link's MAC Addr.

I have turned off the TL-WA850RE and the ARP flooding has stopped.

Regarding moving the TL-WA850RE closer to the router, I don't think it will have any effect since they are connected through an ethernet cable. In fact, they are at very distinct distances: one TL-WA850RE is connected via a 3 m ethernet cable and the other over a 15 m ethernet cable, so the distances are already very distinct and they behave the same.

I guess I will have to throw away the 5 repeaters and buy an Access Point instead. The fact that I went with a "Repeater" graded device is that all Access Points require a separate power supply and something to stand on, whereas the repeaters normally stand by themselves on a wall outlet, making them more convenient since they fit pretty much everywhere. Besides, the TL-WA850RE is also advertised as being able to work in AP mode, and switching a device between AP and repeater mode should never cause ARP flooding anyway.

  @terziyski 

I have never operated the TL-WA850RE on DHCP without a static ip address. All the ARP flooding depicted above with all the 3 different versions of the firmware were run with a static ip address.