Why are DNS requests going the wrong route?

Question

Domain Name System

Good day. There is RB3011 in it 2 providers and a script that pings highly available nodes on each of the providers. If there is no ping, then all traffic through the mangles is transferred to another provider. I noticed an oddity that if provider 2 falls off, then DNS requests stop going normally, and the network falls accordingly. And why I do not understand. Somewhere it can be possible to prescribe routes for DNS?

Answer 1

And what dns are specified? If you use dns provider1, then they may not respond at all to requests that you send through provider2.