Where exactly do you get the rate limiting part from? 100.100.100.100 is provided by the Tailscale daemon on your local device and pretty much all resolving is done locally based on the DNS rules you have configured for your tailnet. MagicDNS will resolve your tailnet clients locally based on the network map, other lookups will be forwarded to your LAN or exit-node DNS or to your configured global DNS servers if you have the override enabled in admin panel.