COREDNS-NSID(7)

✨ COREDNS-NSID ✨

okay so bestie, welcome to the nsid plugin page from the CoreDNS Plugins manual 💅 this one's short but iconic, and honestly it's giving "small but mighty."

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🌸 NAME 🌸

nsid — adds an identifier of this server to each reply. yes, literally that's the whole job and it does it beautifully 🎀

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🦋 DESCRIPTION 🦋

So this plugin implements RFC 5001 ⟨https://www.rfc-editor.org/info/rfc5001/⟩ and it adds an EDNS0 OPT resource record to replies so that each server gets uniquely identified. 🫶

It's lowkey a lifesaver in anycast setups, because you can actually see which server was responsible for generating the reply. Also amazing for debugging — no cap. 🔥

⚠️ Heads up bestie: this plugin can only be used once per Server Block. That's the rule, periodt.

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🧚 SYNTAX 🧚

nsid [DATA]

DATA is the string to use in the nsid record. easy peasy 🍓

And if you don't give DATA? Then the host's name is used instead. default behavior ate, honestly ✨

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💖 EXAMPLES 💖

So here's how you enable nsid — look at this little cutie:

example.org {
    whoami
    nsid Use The Force
}

And now a client with NSID support will see an OPT record with the NSID option, like this:

% dig +nsid @localhost a whoami.example.org

;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46880
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 3

....

; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; NSID: 55 73 65 20 54 68 65 20 46 6f 72 63 65 ("Use The Force")
;; QUESTION SECTION:
;whoami.example.org.        IN    A

like??? the hex literally spells out "Use The Force" 😭 that's main character energy right there 👑

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🌈 SEE ALSO 🌈

• RFC 5001 ⟨https://www.rfc-editor.org/info/rfc5001/⟩ — go read it if you want the full lore 📖

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and that's the whole page bestie, you're officially an nsid expert 💜 this gorgeous little number comes to you from CoreDNS, dated October 2026, in the COREDNS-NSID(7) section of the CoreDNS Plugins manual 🌸🦋✨