Moderator-Julie: Welcome to Network World Chats. Our guest today is Jeff Doyle, celebrity author, Cisco Subnet blogger and networking guru. He has come prepared to answer your questions on all things routing.

Jeff_Doyle: Welcome, everyone! In most every technical meeting I assume I'm the dumbest person in the room, and discussions like this are a great opportunity for me to prove my assumptions correct. Nevertheless, I'll do my best to answer any of your questions. But let me start with a funny little story. I'm in my home office right now, and have had a problem lately with rabbits getting into the office (don't ask). Consequently the office is now my dog Reggie's favorite hangout - several bunnies have met a fast but slightly gruesome end. Hopefully we won't have any "Wild Kingdom" events while in the middle of the chat, but Reggie the mighty hunter is sitting nearby with a keen eye on the utility opening... With that as background, let's get to it.

IPv6 and IPv4

Moderator-Keith: We have a pretty long list of pre-submitted questions that people sent us via the Network World Chat page earlier this week. So while Jeff types answers to your live questions, we'll be posting the pre-submitted questions/answers throughout the chat. Here's the first one:

So, besides the fact that service providers want people to go to IPv6, why should an enterprise deploy it now? If not now, when should it be deployed? Any examples of large enterprises using it in the business world and what kinds of problems did they have to solve before it worked flawlessly?

Jeff_Doyle: Many of my fellow IPv6 advocates hate me when I say it, but I don't think there is much motivation for enterprises to adopt IPv6 anytime soon. IPv6 is important for service providers and any other entities that burn through public IP addresses on a regular basis. All but the largest enterprises don't so that; they can get along just fine behind NAT.

Enterprise interest will rise as they do need new public addresses and they find that the only thing they can get from their provider is IPv6. When it gets to be a bigger hassle to do IPv6 on the outside of a NAT and IPv4 on the inside, they'll start to adopt IPv6. My prediction is that this will happen somewhere in the 2012 - 2015 timeframe.

Moderator-Keith: PRE-SUBMITTED QUESTION: Do you have any recommendations for transitioning to IPv6? Are tunnels or dual stacks better?

Jeff_Doyle: Dual stacks would be better; much simpler, and allow the transition to be driven primarily by DNS. Unfortunately, dual stack assumes that you have both IPv4 and IPv6 addresses. At RIPE55 in Amsterdam a couple of weeks ago, Geoff Huston made the very good point that transition to IPv6 should have been completed before IPv4 runs out, so the transition could revolve around dual stacking. Obviously that isn't going to happen, so tunneling is going to be a key implementation tool. I'm also starting to look more favorably on translators like NAT-PT than I used to; not because I like them, but because they are starting to look inevitable.

Silvia: I have a customer in Italy that has a spaghetti IPv4 network. He is thinking about implementing IPv6 as far as possible instead of fixing the spaghetti network. How would you see the chances for this approach? Is it too early or doable?

Jeff_Doyle: The outlook for him doing this successfully is about as grim as the outlook for those rabbits sneaking into my office. He needs to untangle the spaghetti and get his network under control before adding IPv6, or he will just multiply the complexity. A standard recommendation I make when getting ready for IPv6 is a network inventory and an impact study to ensure the implementation doesn't push the network over the edge.

Moderator-Keith: PRE-SUBMITTED QUESTION: Do software coders need to understand IPv6? What are some of the things they need to know?

Jeff_Doyle: Absolutely. I have a few clients right now who have brought me in to help their developers know what IPv6 standards are important and which are not (within the context of these particular clients' product lines). Which is interesting, because I'm not a coder. For writing the code itself, I always direct developers to the two volumes written by Qing Li, Jinmei Tatuya, and Keiichi Shima, "IPv6 [Core and Advanced] Protocols Implementation."