All Things IPv6

  • Deprecate, Deprecate, Deprecate

    IPv6 has added many new words and ideas to the lexicon of IT professionals.  One of the least expected:  deprecate.

    The dictionary ( says that deprecate means “to express earnest disapproval of”, to “urge reasons against” or, oddly, “to pray for deliverance from”.  In the IT world the world a thing being ‘deprecated’ is a thing being removed from use and (hopefully) replaced with something better.  And many things have been deprecated in IPv6’s journey to replace IPv4 as the mechanism for getting packets from near to far.

    I’m sure the list is longer than even I realize but there are many ideas/implementations/technologies that IPv6 once employed that have since been deprecated.  A few examples:

    IPv4-compatible IPv6 Addresses.  Status:  Deprecated.

  • Know Thy (IPv6) Neighbor

    In IPv6 there are four [tables | lists | data structures] used as part of the packet forwarding process (e.g. Neighbor Discovery and the Conceptual Sending Algorithm).  They are:

    • Neighbor Cache
    • Destination Cache
    • Prefix List
    • Default Router List

    These data structures are currently defined by RFC 4861 (and previously by RFC 1970 and RFC 2461, both now obsolete).  RFC 4861 does a good job describing what these data structures are for and how they should be used but does not, as is typical (and appropriate) to RFC’s, provide any specifics on how they are implemented by each operating system.

    The Neighbor Cache, whose closest conceptual relative in IPv4 is the ARP cache, is primarily a list of IPv6-to-MAC address mappings.  If that were all that was true we could say that the ARP cache and the Neighbor Cache were the same thing.  But they are not.  A Neighbor Cache is much more than an ARP cache.  The Neighbor Cache contains the following information:

  • IPv6 Training Upgrade!

    Our IPv6 training is undergoing  a major overhaul!  The increased demand for this training in the transition to IPv6 is keeping us on our toes! In staying with our philosophy to bring you the best, we strive to keep our IPv6 class as up-to-date as possbile (one of the benefits of writing your own courseware […]

  • Chief Information Officers Council – Roadmap Toward IPv6 Adoption for the Federal Government

    Just last week (July 12, 2012), the Chief Information Officers Council released this updated version of the Roadmap Toward IPv6 Adoption for the Federal Government to help with the upcoming deadlines for September of 2012 and September 2014. It highlights the history as well as the government’s vision for IPv6. To read the original article […]

  • IPv4 Scar Tissue

    I recently read a few articles from around the the Internet regarding the debate surrounding the use of /64 or /126 prefixes on P2P links. Here is a response I left on another site: “The idea of using /126′s is little more than scar tissue from our experience with IPv4. It is the application of […]

  • June 8th 2011 is World IPv6 Day

    June 8th, 2011 is World IPv6 Day! If you aren’t already running IPv6 this is as good a time as any to get your systems set up to play on the IPv6 Internet. Head over to the official World IPv6 Day web site and get going.

  • A Life Without NAT

    Network Address Translation – A Black Mark on IPv4’s Name

    Why do people use Network Address Translation?
    Because they always have, that’s why. “That’s the way we’ve always done it” is one of the dumbest reasons we do things. It precludes continued thought and absolves us the responsibility to think about why we are doing something. Network Address Translation (NAT) has been a bellwether of the Internet world for so long that many of us can’t remember a time without it. Many in the business rally around its role as a mechanism of security in our networks, “hiding the internal network” from the outside world. When presented in such a light it certainly sounds compelling. Being hidden from the evil, nasty outside world? Yeah! I-want-to-go-to-there.

  • IPv6 Means Never Again Having to Wonder…

    …about the IP address of your default router (default gateway in IPv4-speak).

    It’s tough to argue against the fact that most IPv6 addresses are not much fun to type.  Being four times longer than IPv4 addresses and expressed in hexadecimal means things can get ugly on the keyboard pretty quickly.  For people in the IT field one very common mechanism for testing IP connectivity is to ping the default gateway.  And in IPv4 networks, the default gateway is always different for every layer-3 network.  It has now been a thousand bajillion times in my career when I have either asked someone or told someone what the default gateway is for a host who is having connectivity problems.  In IPv6 the ability (or inability) to ping the default router is just as helpful as it ever was in IPv4.  But there are a few apparent problems/challenges:

  • In the World I See…

    I wrote this post several years ago.  By writing it I was trying to get people to begin to think about how the size of the IPv6 address space, when combined with RFID technologies, was going to change everything about how they manage their lives.  I wrote this way before NetFlix began streaming content, before Amazon’s Kindle and before the iPad.  When I recently re-read the post I laughed at how so much of what I wrote was already possible or being done in a completely new and innovative way (e.g. better than I had foreseen).  The sum total of innovation made by forward-thinking individuals continues to take the capacity of technology to places we seldom imagine.  Things once thought laughable and impossible become reality in short order.  So I present the blog post below as a still relevant reflection on where I saw (and still see) things heading.  And here it is:

  • The Debate Surrounding Section

    The IANA (Internet Assigned Number Authority) distributes IPv6 address to RIR’s (Regional Internet Registry’s) around the world. At the moment there are five RIR’s and each of them is responsible for allocating IPv6 address space to ISP’s (Internet Service Providers) and, in some cases, End-User organizations.  Once a block of addresses is allocated to an ISP it becomes their responsibility to distribute the address space to their customer base.

  • On the Practical Feasibility of Ping Sweeping IPv6 Networks

    The IPv6 address space is huge.  On paper each IPv6 subnet (/64) supports more than 18.4 quintillion hosts (millions, billions, trillions, quadrillions and then quintillions).  It’s an amazingly large number.  By every conceivable measure today we can’t contemplate a situation where anything but the tiniest portion of that address space will actually be utilized.  Assuming you never have more than a few hundred nodes on each local segment (a common and best practice using today’s technologies) the randomly generated addresses of your nodes are effectively hidden within the total number of possibilities.  Actually finding one of your nodes using an ICMP ping sweep becomes almost impossible.  We are no longer talking about playing the networking equivalent of Where’s Waldo?, that would be easy.  This is something completely different.

  • Basic IPv6 Resolver Configuration in Ubuntu

    Most DNS servers these days are glad to resolve IPv6 addresses from clients who send the queries packaged in IPv4 packets.  In the grand scheme of things the DNS servers don’t care how you sent the question, they just care about the question.  And because almost everybody still relies heavily upon IPv4, most of us who are trying to push toward IPv6 have been satisfied to get our AAAA resolutions using IPv4 as the transport.  But if you want to start being more ‘pure’ in your IPv6 deployments you need to give your system the ability to not only send IPv6 packets out into the Internet, you also need to learn where it is you are going via IPv6 as well.  Put plainly, you need to configure your system to get its IPv6 name resolution using IPv6 packets.