@MR.S 

  @VolkerS 

upgrade router firmware manualy, the latest version does not notify you in the omada console

https://static.tp-link.com/upload/firmware/2025/202510/20251017/ER7412-M2(UN)_V1.0_1.1.0%20Build%2020251015.zip

  @MR.S 

Thank you for the link.
Unfortunately, I still can't find the ARP option.

  @VolkerS 

If you go to settings and LAN, edit one of the networks, go to advanced settings, it is not there, then your router is not compatible with the new setting.

  @MR.S 

Hello,
Arp is not listed.

  @VolkerS 

If you don't have ARP Detection, your router probably doesn't support it yet. Maybe someone from omadanetworks can answer that?