All KVM VPSes will get a /64 or /80 IPv6 subnet assigned.
During the installation, one IPv6 address will randomly created, and assigned.
Any additional IPv6 addresses will have to be created and configured via the VPS Panel.
In case you VPS has been created before October 2014, and you would like to have a IPv6 subnet, please open a support ticket with the request.
Since the assigned /64 or /80 subnets are being part of a larger subnet (your subnet just administrative assigned), you'll need to specify the shared netmask and gateway.
The details regarding your IPv6 can be found in the VPS Panel, by using the following steps:
1) Log into the VPS Panel
2) Locate your VPS and click on "Manage".
3) Navigate to the tab "Network"
4) Click on your IPv6 subnet, or click on "Manage"
5) On this page you see your assigned IPv6 subnet / gateway and IPv6 DNS resolvers.
When you have a /64 assigned, you will need to use a "/48" netmask
When you have a /80 assigned, you will need to use a "/64" netmask
To apply any changes that have been made, you'll need to click on "Reconfigure Networking", or you can manually edit the network config of your VPS.
When you choose to let the VPS Panel reconfigure your network settings, your VPS will be rebooted automatically.
Below is an example for a /64 allocation to get you started:
In this example you have "2a04:52c0:1234:5678::/64" assigned.
Your full subnet with zeros will look like this:
You can enter any your preffered IPv6 address within the 4x "0000" blocks (0 to 9 and A to F).
Example 1; 2a04:52c0:1234:5678:0000:0000:0000:250 (Short version; 2a04:52c0:1234:5678::250
Example 2; 2a04:52c0:1234:5678:0015:00bf:4523:1000 (Short version; 2a04:52c0:1234:5678:15:bf:4523:1000
In case you still have questions left after reading this "howto", feel free to open a support ticket.