GC110p block traffic between my repeaters

Hi Team,

I am using a GC110p switch and put it between two KPN wireless repeaters with Ethernet cable (which is supported by KPN's guide), but actually those repeaters could not work as a group, they couldn't find each other on their GUI. They arr totally working well when I remove the switch. Same problem when I use GC110 and GC510p instead of GC110p.

I am also trying to find the cause with caputuring traffic with wireshark.

1. KPN repeaters communicate with each other via traffic with protocol 0xfe68 which is an unknown protocol. I use a tool on my laptop which is put with a hub between one of the repeaters and switch, to capute the 0xfe68 protocol packet and change their protocol type to 0x0806 (ARP). But it is not working and they are also blocked by the switch.

2. The destination address used for communicating between KPN repeaters is a multicast address (01:80:C2:FE:03:FE) and it is marked as spanning tree traffic by wireshark. But obviously it is not spanning tree.

Then now I have no any idea about how to investigate more for this problem. It troubles me a lot because the switch is already working at my top floor for all my devices (repeaters, computer, TV...), otherwise I have to design my home network again and it would be a huge effort.

Please help look into this problem and a trace is attached then maybe you guys know how to deal with it.