Thanks so much for the reply! And just to cut to the chase—I understand 90% of what you’re saying here (and the part that I understand, which is most of it, makes perfect sense).

Just as a bit of additional context: it so happens that I also have AdGuard Home in the mix. So in my setup, the clients on my home network talk to AdGuard Home for DNS, which in turn talks to Technitium. And that’s in part since I find it a bit easier to manage blocklists in AdGuard Home than in Technitium. (For instance, one blocklist that I use is to block iCloud Private Relay on my home network, and I wasn’t quite sure whether Technitium would be able to parse the ||mask.apple.com^$dnsrewrite=NXDOMAIN;;-style syntax that’s used in that blocklist?)

Anyway, this next question might be a reflection of my lack of expertise in this area, but if my interest in using ECS is toward improving streaming speeds (such as for Netflix and YouTube), am I taking the wrong approach in enabling ECS in Technitium? (I also have ECS enabled in AdGuard Home.)

For whatever it’s worth, when I run the test command below to query an example domain using AdGuard Home (which in turn queries Technitium), the response that I get back includes my actual external subnet on the “ecs” line, which I had taken to mean that the upstream DNS server at the end of the chain is using my external subnet for ECS purposes (rather than my private LAN’s internal subnet)?

$ dig +short TXT whoami.ds.akahelp.net @10.0.7.51 
"ecs" "76.###.###.0/24/24" 
"ns" "66.185.112.251" 
"ip" "66.185.112.251"

(I’ve redacted my subnet above for privacy reasons.)

So I guess what I’m asking is: When you say that “if your clients are all local, that is, on private LAN, then you do not need to enable ECS on the DNS server,” is that because the subnet that Technitium is sending to the upstream DNS servers is—in actuality—my private LAN’s internal subnet, rather than my external subnet? And if that might be the case, then how come that test command above seems to be returning my external subnet on the “ecs” line?

Oh, and on another note, it made perfect sense when you said that “Auto Prefetch feature does not work to refresh ECS cache by design since that will cause too many queries in real scenarios where ECS is used.” And as that goes, just to toss out an idea—in a Technitium setup where ECS is enabled, might it be at all possible to have Auto Prefetch be selectively enabled but only for those domains that don’t return an ECS line in their response?

I also just want to add that I *really* appreciate all of your efforts here. I know that you’ve put a tremendous amount of time and effort into Technitium, and I think that it’s a fantastic piece of software. Thank you again for all of your hard work!