I've got an AICCU tunnel configured with SIXXS and with radvd on linux, all my machines are connecting and getting IPv6 connectivity. I'm trying to set up a couple of static IPv6 addresses for my servers for DNS and email. If I use the SIXXS subnet address (2001:xxxx), the machines get out but they don't properly register in the Windows DNS server. I've got IPv4 statics on these, but they are trying IPv6 first and failing. I thought that Windows may have some firewall setting that's blocking it, so I used a ULA address. If I set the static IPs to the ULA subnet (fd6c:xxxx), they don't get out at all and still do not register in DNS. Machines that get an autoconfiguration IPv6 address from the radvd router properly register in DNS. It's possible that this registration is being done on IPv4 as they don't have a IPv6 DNS server specified. How should I configure these static IPs? Should I bind both the SIXXS IP (2001:xxxx) and the ULA (fd6c:xxxx) addresses to all my adapters? Is there something special that I need to do in DNS to allow these registrations? It appears that the firewall rules are open and that machines are able to register on IPv4. I'm looking for some best practice information on how to set this up in my lab before puting anything in production. Any guidance is greatly appreciated.