Im using deco m9 plus the apps keep failed to do speedtest. I will stuck on this page, and will pop out mention failed.

Hi, Im using Tm unifi ISP. why my deco m9 plus will auto change the subnet mask format. I see from my apps, WAN the subnet mask 255.255.255.255 while my LAN the subnet mask 255.255.255.0 How ot...