Yesterday I changed my ISP to one that allows port forwarding. Today the port forwarding has been enabled by the company and I set it up on the router.
After enabling it, my download and upload speed dropped from peaks of 50 MiB/s and valleys of 4-6 MiB/s to a very stable 2 MiB/s. Nothing else has changed in my qBittorrent configuration. If I close the ports again, the speed goes back to normal. I checked if the ports were open on various websites and all of them show that they are forwarded.
I was looking forward to be able to port forward and connect with every possible peer for years, and today has been a big disappointment in that regard!
Has anyone else seen something like this and if so, can you point me to the right direction to fix the problem?


I’m not using a VPN. I’m in a country that doesn’t really enforce piracy laws if you are not making a profit.
Are you manually setting your DNS?
No! Should I?
yes, and you should also be using a VPN because it sounds like your ISP is throttling that port because you asked for it to be open and they know what you’re doing with it. either that, or they just automatically throttle bittorrent traffic that their systems sniff out. pick a VPN that allows port forwarding.
And if you pick a vpn that does, it doesn’t matter if your ISP does.