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As I have come to understand, SSH always goes through the process of reverse DNS lookups whether you are connecting to
email@example.com or a local server called
firstname.lastname@example.org. I do not know, however, why the SSH command performs a reverse dns lookup for IP addresses regardless. Like, I had to change my DNS server configuration on my Pi to Google's open DNS so that my client machine wouldn't take so long to actually handshake with the server through DNS lookup with my ISPs DNS servers. Even when my Pi is on my local network.
tl;dr - Why does SSH do reverse DNS lookup for local IP addresses?