Dude about new dns

Hello, I don’t know if I am in the right place I have a question I am a user of the primary dns and secondary also and respectively I am trying to use them in an access point but only the secondary ones work for me, is there any explanation for this? thanks in advance

Lots of equipment and networks still use (and internally. Cisco for example used as the WLC address for years, and plenty of public wireless networks used as a captive portal address. There is a Blog post about Cloudflares effort to debogonise the address space.

What type of equipment are you using?

Thanks for answering It is a listed router and an AP, but I see that it is a thing of that router
It has helped me a lot, thank you very much.