I am running a Asus router with Asus WRT-Merlin as the firmware.
Until recently I always used Google's DNS servers of 18.104.22.168 and 22.214.171.124 rather than my ISP's as I thought for international traffic there was a slight speed improvement and that has worked fine for years.
However I recently moved to a new property and as per usual was using the Google DNS servers and everything is fine for a few days until my broadband starts getting really slow and if I go and change the DNS servers to automatically use my ISP's the broadband speed goes back to normal again for a few days until the same thing happens and then I again switch back to Google and keep repeating this process for months now.
I am fairly technical when it comes to networks but I can't figure out why this would be the case that I have to change the DNS servers three times a week to keep my broadband speed consistent. I know that DNS servers could be experiencing a slow down so it makes sense to switch DNS servers for a while but to have to repeat this on such as regular basis seems to apply there is a something else up with either my broadband connection as a whole or my router. It's not such a hardship to make the change but would rather not have to do it if I can avoid it and I am more curious than annoyed with the situation.
If someone has any ideas about what is going on or ever heard of something similar before?
Doubt it helps or makes a difference but previously I have always lived in a city with fibre to the cab in the street and then copper to the house and I was less than a mile from the telephone exchange were as now I live in more rural location and probably around three miles from the exchange and all of that served over copper. Because of the rural location my broadband is half the speed of my previous property but it's still around 40mbp/s so speed isn't a issue until it starts to crawl and then I change the DNS and it's immediately back to full speed.
Anyway would greatly appreciate any help in solving this slightly annoying mystery.