Destination Port 3478



I notice in my router logs that there are a lot of block requests to port 3478 (UDP and TCP:S) on IPs associatd with dns.nextdns.io (e.g.

Does anyone know what this traffic is and whether I should allow it?


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  • Port 3478/udp is often used for STUN, which can be used by services to help setup real time communications channels (voice, video, even real-time data) when NAT is involved. Do you the NextDNS logs page set to auto-refresh or anything like that while you see this? I cant think of anything else on the NextDNS site itself that would do that, and actually since it’s not going to my.NextDNS.io, I am probably totally off-base here.

  • Chris Leidich  Thanks Chris, Yes I am aware STUN uses port 3478, though curiously only my router is running nextDNS and the source address is associated with my pc which isnt running nextDNS (it uses the router for DNS). So I am wondering also if it is something to do with their webpage, though I don't remember if it was even open when I saw the traffic. Odd.

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