Netgear: Ipv6

IPv6 is all dependent on your ISP (And if your router / modem supports it) the best way to set it up is first contact your ISP ask them if they support it and if your network plan is allowed to use it. If so then check if your router / modem supports it.
If it does then great! Enter your IP address into the search bar and hit enter (Ex: 192.168.0.1 or 1.1 please take note that you cannot sign into a router / modem if you are not connected to it) there should be a login in screen your ISP will provide the info.
Look around and try to find the switch from IPv4 to IPv6.

http://support.xbox.com/en-CA/xbox-one/networking/ipv6-on-xbox-one

Contact your net provider to verify if your connection can handle IPv6

IPV6 has to be supported by your router and your ISP. IPV6 is already built into Xbox and when it detects it you're set.

Comcast is my ISP and their network supports IPV6.

I have a netgear router that supports IPV6 and it's just a matter of logging in to the router and enabling the IPV6 feature.

https://beta.support.xbox.com/help/Hardware-Network/connect-network/ipv6-on-xbox-one

For Xbox One to connect to the internet using IPv6, your home router needs to have IPv6 enabled, and your internet service provider (ISP) must support IPv6.

Is your router a Netgear as well or is it from your ISP? If it is a Netgear here is a link to the steps to enable IPv6.

https://kb.netgear.com/24006/How-do-I-set-up-an-IPv6-Internet-connection-on-my-Nighthawk-router

If the router is from your ISP then you should contact them to get assistance in changing it if you can't do it form the Admin on your network.

Could you please verify the make and model number of your router.

For clarity, what is make and model of your modem?