You see AS3356 in traceroutes far more often than as an end point. Its public resolvers 4.2.2.1–4.2.2.6 were once widely used as an alternative to ISP DNS and still answer today, though Lumen no longer promotes them.
Networks (ASN) / AS3356
AS3356 Lumen Technologies (Level 3)
Tier 1 backboneUS
Formerly Level 3 Communications: one of the largest Tier 1 internet backbones, carrying traffic between other networks worldwide.
Frequently asked questions
Is 4.2.2.2 a good DNS server?
It works and is fast in North America, but it is an unofficial service with no published privacy policy. Prefer 1.1.1.1, 9.9.9.9 or 8.8.8.8.