IPv6 address preference in Windows 8
I had a stupid IPv6 problem. I’d shrunk the block I assigned to my LAN from a /64 to a /120 to stop autoconfigure. Autoconfigure will only happen on a /64 netmask. I did this so I could only have some devices run IPv6 that I assigned manually. IPv6 will be preferred to IPv4 if there are routes.
Because it has priority, Netflix and youtube will go IPv6 and because I’m tunneled for now via Hurricane Electric, it chokes. In the process of making some changes and testing, I had temporarily set the /64 back on the Cisco LAN interface. My windows 8 host, immediately grabbed some addresses ( as probably did a bunch of devices on my network )
I then put the router back at /120 and could not ping out ipv6 to Cisco or Facebook. I could ping in, just not out. I finally trapped it on a remote host with wireshark and saw an unreachable from a /64 address my Win 8 box had autoconfigured. I bounced the Win8 interface and poof it all worked fine again.
Windows 8 was preferring the /64 address to the /120 address on the same block, which seems stupid. I’m not sure if it prefers a ‘higher’ IP or such, but I would have thought it would prefer the more specific mask. I need to read up to see why it preferred sending from the /64 autoconfigure to a static /120 when both were active.