IPv6 is basically the response to the fact that the world is/was running out of public ip addresses. The best example of stupidity leading to the problem is universities handing out public IP address to students and facility on their networks. A corporation would be insane to hand out public ip addresses to staff members.IPv6 default subnet is 255.255.255.255.0Ipv6 has 5 octets - 255.255.255.255.0Ipv4 has 4 octets - 255.255.255.0Personal OpinionIpv6 is not failure as such. I'm sure it's implemented somewhere, but I've not seen it. The solution to running out of IP addresses is better management of IPv4 addresses. Hardware/IOS manufactures often use 10.0.0.0 (called a '10' network) in examples of how to configure their devices. The students then return to their networks and implement their text book learning's in their networks. BIG MISTAKE! Then these students wonder why things are all messed up on their networks. You should Class 'C' addressing on your private, smaller networks. It'll work out much better for you.