While setting up 2008 Clustering on vSphere I came across an annoying error saying that I had a duplicate IP on what seemed to be an unknown Ethernet interface.
After some poking around I managed to find a few articles that pointed me in the right direction. The problem is related to Teredo, which is an IPv6 Tunneling Protocol. It allows IPv6 communications to pass through IPv4 NATs and IPv4 servers. It ends up giving an identical IP address to its network interfaces, and that's what causes the problem.
