I purchased and install the latest version of NordVPN today. I noticed that my IPv6 whch had been working fine was no longer working, as NordVPN either breaks or disables IPv6. Anyway I contacted their Tech Support while finding the following on their website dating to 2017:
"In a nutshell, if a NordVPN customer were to have an IPv6 IP address, their IPv6 interface would be blocked and only IPv4 traffic would be rerouted and encrypted with NordVPN, which ensures that your real IP address never leaks.
Technically speaking, when establishing an OpenVPN connection, our clients add additional routes. IPv6 traffic is effectively rerouted to a “black hole” within the device. This feature happens by default on all NordVPN applications that use OpenVPN, requiring no user action. IKEv2/IPsec protocol does this automatically. Up next, we plan to tackle the IPv6 support on our servers – follow our blog for updates on the topic." Tech Support more or less verified this.
So essentially here it is almost 2019 and NordVPN still doesn't support IPv6. It deselects IPv6 on your Wifi Adapter properties settings. This is on Windows 10 1809+. I just thought that people who really need IPv6 ( I don't think I currently do) that they might want to be made aware of this. Also in case that you don't know, this NordVPN also reduces my speed throughput by up to 20%. I usually test out, on wireless, at 235/11.....or in that ball park.....Its more like 200-210 now. I do not know of any other VPN products if they also have these "features". HTH
p.s. I forgot to add I had to completely turnoff the IPv4 and IPv6 firewalls in my Technicolor TC8717t gateway modem/router to even get a VPN connection. Luckily the Windows 10 default firewall allows connection with no rules or setup required.
This information is important for anyone who chooses to operate with NordVPN software. Thanks for posting it to the forum. The slight speed decrease that you see reported by Speedtest is normal.