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The original was posted on /r/wireguard by /u/dark_tex on 2023-12-29 18:03:27+00:00.
I installed a Pi4 at my parents' house to be my Wireguard server (using pivpn).
Everything works great if I keep the server's IPv6 address in the client's config file, but I get abysmal performance (many websites wouldn't even load, others would load but bandwidth would be excruciatingly low) if I don't.
Why not keep it, then? Well, I'd like to deploy this to my Unifi network (ideally using their newly-released integrated client instead of udm-utils and the likes so that it can survive updates) and unfortunately they don't seem to like IPv6 in Wireguard config files. When I uploaded the config file, Unifi was complaining that the IP address of the server was in the wrong format, and the only way I got it to work was by deleting the v6 address.
I know that this is the root cause because if I delete the v6 address and connect on my Windows client, I get the shitty performance. Add it back and voila we are flying again.
I have no idea why this happens though, and why *some* websites work (albeit slowly) while others never load at all (traceroute doesn't know where to go). Perhaps my parents' ISP has some weird ass configuration?
How would you proceed from here? I'd be interested in workarounds, but I have to say that I am generally curious to learn more about networking and this could be a great opportunity to further my understanding of networks. So, if you wanted to learn more about _why_ this happens and what's really going on, what would your next steps be?