After playing with IPv6 extensively over the weekend, I discovered a number of oddities about the protocol.

First, autoconfiguration only works with /64 subnets. Anything more or less, even if the router advertises the prefix, clients will not add the prefix to its own interface. This seems like it can problematic as users cannot easily break down these prefixes into smaller subnets. This could be a key area for using DHCPv6 as a replacement.

Second, autoconfiguration will not work if the computer is configured as a router for IP forwarding. This means that additional work for defining routes needs to be done even if you only plan on using the default gateway on a network. This can either be in the form of static routes or a full blown routing protocol.

Third, 2002::/16 (IPv4 transition addresses) doesn't count as a real IPv6 address when source address selection occurs. Instead it is considered a separate scope, similar to an IPv4 address. This means when websites have both a 2001::/16 IPv6 address and a IPv4 address, the IPv4 address is used by default. If the website has a 2002::/16 IPv6 address and a IPv4 address the 2002::/16 IPv6 address is used to connect. This seems very odd and inconsistent and can lead to confusion.