Also, the service supports IPv6 DNS queries from end-users ... such as 1.1.1.1 for Cloudflare. If nslookup returns errors using multiple servers, this doesn't look like a DNS issue.

Route optimization helps improve internet speeds by avoiding outdated servers or heavy traffic. Google DNS, OpenDNS, and ...

The DNS server provided by your ISP may not be the fastest or most secure option. Google DNS, OpenDNS, and Cloudflare are excellent free DNS servers that can enhance internet speed and security.