How to turn off IPv6 in Sierra

ok this is how:

Open your Terminal app. Type the command:

networksetup listnetworkserviceorder

There will be a list of all the network devices. In my case it was:

An asterisk (*) denotes that a network service is disabled.

(1) MT65xx Preloader

(Hardware Port: MT65xx Preloader, Device: usbmodem1340)

(2) Ethernet 1

(Hardware Port: Ethernet 1, Device: en0)

(3) Ethernet 2

(Hardware Port: Ethernet 2, Device: en1)

(4) Thunderbolt Ethernet Slot 2

(Hardware Port: Thunderbolt Ethernet Slot 2, Device: en10)

(5) iPad USB

(Hardware Port: iPad USB, Device: en12)

(6) Wi-Fi

(Hardware Port: Wi-Fi, Device: en2)

(7) iPhone USB

(Hardware Port: iPhone USB, Device: en11)

(8) Bluetooth PAN

(Hardware Port: Bluetooth PAN, Device: en9)

(9) Thunderbolt Bridge

(Hardware Port: Thunderbolt Bridge, Device: bridge0)

Then you can disable ipv6 using the above name like this:

networksetup -setv6off "Ethernet 1"

Be sure to quote the device name if it has spaces in it.

See this article macOS Sierra: Set up a 6to4 network port configuration

To disable it completely you need to use the Terminal app

Open Applications, Utilities Folder, Terminal

To disable IPv6 on your WiFi interface type:

networksetup -setv6off Wi-Fi

To disable IPv6 on your Ethernet interface type:

networksetup -setv6off Thunderbolt Ethernet

To get back default settings:

networksetup -setv6automatic Wi-Fi

networksetup -setv6automatic Thunderbolt Ethernet

Michaels-Mac-Pro:~ MGW$ networksetup -setv6off Ethernet

Ethernet is not a recognized network service.

** Error: The parameters were not valid.

Michaels-Mac-Pro:~ MGW$ networksetup -setv6off Thunderbolt Ethernet

Thunderbolt is not a recognized network service.

** Error: The parameters were not valid.

Any idea how to find the correct parameter?

Goto 'System Preferences', 'Network'. Select network interface you want to change, for example WiFi. In the right bottom pane select 'Advanced', goto tab 'TCP/IP' where you have options to configure IPv6. By default it's configured to 'Automatic', I think if you change it to 'link-local only' will do the trick.

BTW do you happen to know of any DNS services that have a work around for the Ipv6?

I think you have to look at a VPN service, I can't recommend any as I don't use them, try a search engine for more info. Think it's also out of scope on this Apple Support Community to discuss it.