Lets rant about IPv6 a bit? Might be more articles in future.
IPv6 is easy to setup if you have BGP or your upstream is willing to cooperate in any imaginable way (static routed, bgp default, bgp full). If you don’t have upstream on Layer2 direct you don’t deserve to host anything for anyone. No excuse.
Elementary: Your switching has no IPv6 support?
Nobody runs this still, if you do then you don’t deserve it to host anything for anyone. Buy new switches. NOW.
24x1GE/2SFP – HP 1910-24 – 150EUR with VAT
48x1GE/4SFP – D-Link DGS-1210-52 – 250EUR with VAT
You don’t need more than that, if your old switches have no IPv6 they don’t have 10GE or more than 1000Mbit uplink anyway. No excuse.
Your routing equipment has no IPv6 support?
What the hell are you running on? If you are a DC this is not an excuse is any possible way – A IPv6 default route and some 100-1000Mbit work on *anything* that has a brand and can take 2x full BGP (which is the bare minimum for any DC, else its a basement.)
VLAN assignments are easy as pie, just assign each VLAN a /48 and send the customer info for a /64 for each device in his VLAN, maybe write something to assign him a /64 and gateway on a software router (or, if you are a modern DC on your ToR switch) with a webpanel even. No excuse.
Flat layout or MAC filtered networks (+ vodoo) (OVH/Hetzner as examples) can just roll out a shared infra with smaller assignments (due to MAC tables) and then later switch over to VLANs and route this smaller networks (like /112s etc.) inside VLANs as they do with the IPv4 space. No excuse.
There is no excuse to not offer IPv6 in 2013. Not for anyone that offers VPS/Dedicated servers. Webhosting has a grace period still with many due to HA setups lack of v6 (L7 and alike) but this ends soon as well. Not it’s on the end-user ISPs.