Root on loopback (RFC 7706)

Knot Resolver developers think that literal implementation of RFC 7706 (“Decreasing Access Time to Root Servers by Running One on Loopback”) is a bad idea so it is not implemented in the form envisioned by the RFC.

You can get the very similar effect without its downsides by combining Cache prefilling and Serve stale modules with Aggressive Use of DNSSEC-Validated Cache (RFC 8198) behavior which is enabled automatically together with DNSSEC validation.