/64 routed to my assigned IPv6 address?

Solution 1:

Welcome to the wonderful world of having far more IP addresses than you'll ever know what to do with. (And good on your VPS provider for doing it right and assigning you a /64 instead of something smaller, which a lot of misguided providers seem to be doing...)

One purpose, as you may have guessed, is so that nobody ever runs out of IP addresses, ever. Or at least not for a very long while...

So this is how it's going to work for you:

1. Your IP address assigned to eth0 interface is 2607:f840:0:3f::eaa. This is on the upstream provider's /64. When packets come in for your subnet, 2607:f840:44:22::/64, your upstream provider routes them to your eth0 interface.

2. What you do with the packets when they arrive is entirely up to you. Since you're on a VPS you probably don't need a whole lot of addresses, so you could just start assigning them from ...::1 to your existing eth0 interface.

   For example:

   ip addr add 2607:f840:44:22::1/64 dev eth0
   ip addr add 2607:f840:44:22::2/64 dev eth0
   ip addr add 2607:f840:44:22::3/64 dev eth0
   ip addr add 2607:f840:44:22::deca:fbad/64 dev eth0
   ip addr add 2607:f840:44:22:feed:face:dead:beef/64 dev eth0
   

   If you're further dividing your VPS into containers (e.g. OpenVZ or LXC) then you could route the /64 to the network bridge which will serve the containers, and assign addresses to the containers.

See also the closely related question, How does IPv6 subnetting work and how does it differ from IPv4 subnetting?

Solution 2:

Let me answer by quoting from RFC 5375: IPv6 unicast address assignment considerations

Using a subnet prefix length other than a /64 will break many features of IPv6, amongst other things Neighbor Discovery (ND), Secure Neighborship Discovery (SEND) [RFC3971], privacy extensions [RFC4941], parts of Mobile IPv6 [RFC4866], PIM-SM with Embedded-RP [RFC3956], and SHIM6 [SHIM6]. A number of other features currently in development, or being proposed, also rely on /64 subnet prefixes.

Your provider is simply sticking to safe standards. You get a huge address space to work with, but that is a good thing. It makes things future proof.