While there is nothing inherently wrong with what you are proposing, you may not be taking sufficient advantage of the available address space. Subnets are no longer a scarce commodity, and you want a v6 design which is resilient in the face of the next 15-20 years worth of anticipated changes. There isn't a lot of consensus on any particular One True Way of assigning v6 address space. What consensus there is revolves around simple truisms like start in the middle and work out both ways; align on 4-bit nibble boundaries to ease documentation and reverse DNS; leave unallocated reserved space between things you are using, etc. It's good to use things with semantic significance, and to avoid embedding v4 subnets, layer 2 vlan tags, or other ephemera just because they would happen to fit and would look cute. You're already doing all that.
> I read somewhere that I need to reserves the first (or the last) block of IPv6
> prefix for network devices, servers and point-to-point links and loopback.
This is an oft-followed convention, not an actual requirement. But by all means continue it. A current convention is to give each point-to-point link its own /64 in the addressing plan, but to operate them as /127's.
In my case, it took me 3-4 design tries to come up with something I liked well enough to deploy in production. The UW-Madison eventually ended up with a PI /32, from which my sub-organization was allocated the usual /48. I'm only dealing with a handful of sites, so with 16 subnet bits WXYZ to play with, I'm using W for routing /52's to sites, reserving X, using Y to distinguish various kinds of subnets, and keeping Z mostly reserved for when semantically similar subnets split more finely. E.g. my DMZ subnets use Y=5, leading to 1050 in one building, 2050 in another, and 2058 when a VPN server moved out of a main DMZ into its own uplink subnet. My most likely changes are more subnets and vlans for security reasons, or a few more buildings, both of which kinds of changes are easily accommodated. If there were a sudden proliferation of sites, say the state of Wisconsin told us to put satellite labs in 70 county health departments, I could switch to routing /56's, or break on-campus versus off-campus routing at a /49 or /47 boundary - an adjacent /48 is reserved for me by my parent organization, but not allocated.
The main thing is to consider your organization needs, and their likely changes, and build a network design which adapts easily to those changes without requiring a lot of renumbering or documentation updates. E.g. in v6 (but not v4), I can and do number semantically similar vlans with the same Y value across the subnets in all buildings, which makes my documentation and QA a lot simpler.
You are off to a good start; just don't be afraid to take some time to think about it before fully committing to a particular design.
-- Jim Leinweber, WI State Lab of Hygiene
