@kerykeion 

I understand that you noticed the 5GHz_2 band is unchecked in your Deco X90's WiFi advanced settings, while the 2.4GHz and 5GHz_1 bands are enabled, and you're wondering if the 5GHz_2 is dedicated to wireless backhaul.

According to our knowledge base, your Deco X90 is a tri-band system with three radio bands:
• 2.4GHz band: up to 574 Mbps
• 5GHz_1 band: up to 4804 Mbps  
• 5GHz_2 band: up to 1201 Mbps

Your understanding is correct. The 5GHz_2 band that appears unchecked in the WiFi advanced settings is typically reserved for wireless backhaul communication between your Deco units. This dedicated backhaul band helps ensure that the mesh communication between Deco units doesn't interfere with your client devices' WiFi connections on the 2.4GHz and 5GHz_1 bands, which optimizes overall network performance.

The 2.4GHz and 5GHz_1 bands that you see enabled are the ones available for your client devices (phones, laptops, tablets, etc.) to connect to, while the 5GHz_2 band works behind the scenes to maintain a strong mesh backbone between your Deco units.