layout first:
2 internet connections. 1 Cable and 1 DSL
5 buildings, each building has own subnet (ipv4 /24) and want to give each building own /64.
The problem is that I'm getting a different /48 routed through each tunnel. Can I set 1 tunnel as the primary and 1 tunnel as the secondary route of an he supplied /48?
You can definitely set two /64 networks in each building. I'm not sure if you can prioritize them differently, or get any sort of failover.
In any case, I don't think that is what you want. I think you may want a pair of BGP tunnels to route one network through paths with different priorities. I'm not sure of the details there, or where you get the assignments. This would allow you to have one netblock, two tunnels, and automatic failover and sharing between them.
Alternatively, if you already have a public IPv4 netblock that can route through either connection, then you could just have one tunnel routed over the existing IPv4 infrastructure.
My suggestion: write to ipv6@he.net, describe your situation, and ask for advice.
Third possibility:
Make one tunnel. Use it normally over the better IPv4 connection. When/if that fails, use the dynamic address capabilities of the tunnel to reconfigure it to the other IPv4 connection. If the monitoring is good enough, you probably won't even lose IPv6 connections.
--David
Do you just want two tunnels because you have two ISPs? In that case, you'll need BGP
If you can live with only having one tunnel, this becomes easy.