Thanks guys, this is what I have come up with so far. Next week i'll put together a web page or something with slightly better write-ups, but these are my initial ideas for responses to each point. Better answers would be welcome. "We have NAT, therefore we don't need IPv6." "We still have plenty of IPv4 addresses" "IPv4 works so we don't need IPv6." They said similar things about IPX, DECNET, Appletalk........ but they eventually realised it was easier to move to IP than to keep making excuses for why their network can't connect to anything. "we want NAT for IPv6 for security reasons" NAT does not provide any security, typically a NAT will also include a stateful firewall which provides the security. You can deploy a stateful firewall for your IPv6 network if you like, however it isn't required as much as you probably think it is - see below. "IPv6 is just another way for hackers to get in." There is no difference between IPv4 and IPv6 when it comes to firewalls and reachability. It is worth noting that hosts which support IPv6 are typically a lot more secure than older IPv4-only hosts. As an example every version of Windows that ships with IPv6 support also ships with the firewall turned on by default. "End users don't care about IPv6" Are you saying this in response to someone asking for IPv6? because that would be contradictory. I am an end user and I care about IPv6! "But it isn't a priority and we have other stuff to do" Reconfiguring every router on your network is not something you want to rush when you realise you needed IPv6 yesterday, early adopters have the advantage that they can gain experience with running IPv6 and test their infrastructure without worrying about critical traffic being IPv6-only. "None of the software vendors support IPv6." If your software vendors were following best practices and writing decent code then this would not be a problem, I suggest pushing your vendors to fix their code. If you only have 1 of two systems that are IPv4-only then you can always "special case" them. See NAT64 for information about one way of reaching IPv4 hosts from an IPv6 network. If you dual stack then it doesn't matter and you can just use IPv4 for those few services than require it until you get a fix from the vendor. "None of our staff understand IPv6." Do your staff understand IPv4? because it's not that different... "IPv6 addresses are too long to remember" You shouldn't need to remember IP addresses, that's what DNS is for. However I will say that in my experience and many other peoples having the extra bits to structure your network in a logical fasion can make addresses more obvious and easier to remember. You have a single prefix to remember, then can address hosts within that subnet however you like. In IPv4 you rarely have the luxury of being able to number your DNS server 192.0.2.53 and your web server 192.0.2.80 to make them easier to remember, whereas in IPv6 you can easily assign hosts easy to remember addresses. "Having to dual stack means I still have to manage a 4 and 6 network." Good point, however if you want to ease your network management and run an IPv6-only network with IPv4-only services still reachable over the top of it then there are several ways to do it, the most obvious being NAT64. "Our DNS provider won't let us as add AAAA records" Seriously? who is your DNS provider? You need to ask them why they don't support standard record types. If they refuse to add standard records to your zone, get a new provider there are plenty out there. "We'll deploy IPv6 right after we finish deploying DNSSEC" The 2 are not mutually exclusive - at a large organisation where this sort of project would be major work, you probably have different teams dealing with IP and DNS so there's no reason one would stop the other. "But Android doesn't support stateful DHCPv6." I will admit that the specifications were written a little loosely so you have 2 ways of configuring hosts, however if you configure both RA and DHCP then you will cover 100% of IPv6-capible hosts. "Our legal intercept setup does not work with IPv6" If your lawful intercept equipment can't see traffic just because they used an "unknown" protocol then it has a major flaw! - Mike Jones