Some public/recursive DNS Servers like Cloudflare (1.1.1.1) do not tell the authoritative dns server the ip address or subnet of the requestor. Your ISP's DNS server usually does this. This makes CDN via DNS more difficult, as it is not always entirely clear from where the request comes (Cloudflare itself does not need this, they do everything with Anycast).
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Some public/recursive DNS Servers like Cloudflare (1.1.1.1) do not tell the authoritative dns server the ip address or subnet of the requestor. Your ISP's DNS server usually does this. This makes CDN via DNS more difficult, as it is not always entirely clear from where the request comes (Cloudflare itself does not need this, they do everything with Anycast).