About wrong interface, it has bridge interface that link all ether1-5 After days of browsing online I found a tool called tcpdump. I use it on one end tcpdump -i eth0 'udp port 51820' 15:07:47.474818 IP ezecom.45.118.222.0.149.ezecom.com.6163 > h.wireguard_server.com.51820: UDP, length 148 15:07:51....