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[*]We have fiber at 300 Mbps up & down. I’ve run several different speed tests, and all but one came back at almost 400 up and down, decent latency too. I know it’s hard for others to believe (I didn’t at first) but speed test doesn’t show this issue. Our previous Comcast 25 Mbps service loaded webpages much faster than the new AT&T 300 Mbps service. We were getting “lost connection” about a half dozen times/day, that almost never happened with our old slow Comcast connection up north. ...
What is 'decent'? Can you run a basic ping command from a console/terminal? That will give you raw numbers, rather than something that might be "translated" as good/fair/poor or something. And ping your DNS (and make sure you know what DNS is being used by each router).
This might be it: Your old router might be set to use a different DNS than the AT&T supplied one, and it might not be easy to verify the AT&T DNS?
I'm not sure I follow - are the 'lost connections' on your current set-up? With either router? This went away? Or an older set up? Or are you on AT&T 300 now, and were on Comcast 25 at this current location? The "comcast" and "up north" makes me unsure of all this. You had comcast at both places, but only drops now in the 'south'? But web pages loaded OK?
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[*]I thought it might be our old iPads that were contributing to poor performance - until I took my iPad to Starbucks and got MUCH better performance on their 40 Mbps WiFi vs my home 300 Mbps WiFi! ....
This is irrelevant and distracting you from the problem - and the sooner you get this thinking out of your head, the better you will be at troubleshooting these sorts of issues.
A "bigger number" is not always better. Most web pages will download plenty fast on a far slower connection. You really only need the higher rates for some streaming, and even at that, multiple streams (or DL large files). So 40 Mbps versus 300 Mbps will mean nothing to a typical page load time.
This is like putting 180 mph rated tires on a stock Model T, and being surprised that it didn't affect the top speed. It's not the weak link, look elsewhere!
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[*]Again, I don’t think signal strength or interference have anything do do with it. Phone support told me I needed a $50 range extender, that they were detecting interference (from India) - pure BS IMO. But we have full bars on WiFi signal and I can stand next to their AT&T router and it doesn’t help at all.
I can easily just use my modem for everything, just wondered if splitting would provide better performance with several devices on simultaneously.
Might not be BS at all. Interference can show up as 'retries', and that *might* be detectable remotely. I'm pretty sure that if some data gets dropped or an error is detected, the router just requests for that data to be re-sent. So this can really slow down response, but everything is happening at a high speed. Maybe someone closer to network protocols can confirm/deny that.
If everything is working well with the two routers, why not just leave it? I might want to shut down their router if it isn't working well, as it might interfere with your router, or at least keep them on different bands?
-ERD50