My network provider has allocated me a IPv6 /56. My goal is to give a /64 to each virtual machine I have. They told me they would route the /56 to my CentOS Xen server and I would have to handle the routing to the VMs.
Do I assign 2001:db8:1111:15::2 to the host server's network config with ::1 being the gateway?
Message from provider:
We have routed the IPv6 addresses to you vlan.
2001:db8:1111:15::1/122
Then we routed
2001:db8:2222:2000::/56 to 2001:db8:1111:15::2
Yes, my reading of the provider's response is also that you configure your physical interface with 2001:db8:1111:15::2/122 using 2001:db8:1111:15::1 as the gateway.
Using a /122 for the link prefix is a bit unusual. The recommended practice is to use a /64. But you shouldn't configure a shorter prefix than the provider told you to, so I recommend you stick with /122 like they said.
The good news is that since you got a routed prefix it isn't a big deal for you how the provider chose to configure that link prefix. An earlier question has more details on link prefixes and routed prefixes.
The routed prefix 2001:db8:2222:2000::/56 can be subdivided into 256 link prefixes allowing for up to 256 VMs. Though you might want to set aside some /60s in case you find a need for a routed prefix on one of the VMs.
For example you could use 2001:db8:2222:2000::/64 through 2001:db8:2222:207f::/64 as link prefixes to allow for 128 VMs. And use 2001:db8:2222:2080::/60 through 2001:db8:2222:20f0::/60 as routed prefixes allowing for up to 16 of your VMs to get a routed /60 for themselves.
