How-To Geek

What Is IPv6, and Why Does It Matter?

IPv4 addresses on the public Internet are running low. Microsoft paid $7.5 million for Nortel’s 666,624 IP addresses when Nortel went bankrupt in 2011 – that’s over $8 an IP address. IPv4 has technical problems, and IPv6 is the solution.

Unfortunately, deployment of IPv6 has been put off for too long. Had IPv6 been implemented years ago, the transition from the older standard to the newer one would have gone much more smoothly.

Image Credit: Bob Mical on Flickr

Technical Problems with IPv4

In 1980, Internet Protocol version 4 addresses were defined as 32-bit numbers. This provided a total of 232 IPv4 addresses – that’s 4 294 967 296, or 4.2 billion, addresses. This may have seemed like a lot of addresses back in 1980, but today there are many more than 4.2 billion network-connected devices on the planet. Of course, the number of devices connected to the Internet will only continue to grow. To make matters worse, some of these IPv4 addresses are reserved for special cases, so the Internet has fewer than 4.2 billion publically routable IPv4 addresses available to it.

There aren’t anywhere near enough publically routable addresses available for every device on the Internet to have a unique one. One thing that’s helped is network-address translation (NAT), which most home networks use. If you have a router in your home, it takes a single publically routable IP address from your Internet service provider and shares it amongst the networked devices in your home. To share the single IPv4 address, it creates a local area network, and each networked device behind the router has its own local IP address. This creates problems when running server software and requires more complicated port forwarding.

ethernet cables

Carrier-grade NAT is one solution – essentially, every computer using an Internet service provider would be on a local network specific to that ISP. The ISP itself would implement network-address translation, just like a home router. Individuals wouldn’t have publically routable IP addresses and running some forms of server software that requires incoming connections wouldn’t be possible.

Image Credit: Jemimus on Flickr

How IPv6 Solves the Problems

To avoid the future exhaustion of IPv4 addresses, IPv6 was developed in 1995. IPv6 addresses are defined as 128-bit numbers, which means there are a maximum of 2128 possible IPv6 addresses. In other words, there are over 3.402 × 1038 IPv6 addresses – a much larger number.

In addition to solving the IPv4 address depletion problem by providing more than enough addresses, this large number offers additional advantages – every device could have a globally routable public IP address on the Internet, eliminating the complexity of configuring NAT.

unplugged ethernet cable

Image Credit: Justin Marty on Flickr

So What’s the Hold Up?

IPv6 was finalized in 1998, 14 years ago. You might assume that this problem should have been solved long ago – but this isn’t the case. Deployment has been going very slowly, in spite of how long IPv6 has been around. Some software is still not IPv6 compatible, although much software has been updated. Some network hardware may also not be IPv6 compatible – while manufacturers could release firmware updates, many of them would rather sell new, IPv6-ready hardware instead. Some websites still do not have IPv6 addresses or DNS records, and are only reachable at IPv4 addresses.

Given the need to test and update software and replace hardware, IPv6 deployment has not been a priority for many organizations. With enough IPv4 address space available, it’s been easy to put IPv6 deployment off until the future. With the imminent exhaustion of available IPv4 addresses, this concern has become more pressing. Deployment is ongoing, with “dual-stack” deployment easing the transition – modern operating systems can have both IPv4 and IPv6 addresses at the same time, making deployment smoother.

Chris Hoffman is a technology writer and all-around computer geek. He's as at home using the Linux terminal as he is digging into the Windows registry. Connect with him on Google+.

  • Published 07/22/12

Comments (32)

  1. Cory

    I havent heard one good explanation from anyone I’ve talked to about why it’s important for things in my house to have a globally routable and public IP address instead of my own private NAT that I have much more control over.

    Private NAT setup is not difficult in the least, most of the tech issues rise around accessing the Wifi for various reasons, but the NAT works great for everything I’ve thrown at it.

  2. Sandeep

    Why is IPv4 not called v5? Likewise, why is v6 not called v7?

  3. Paul

    “there are over 3.402 × 1038 IPv6 addresses” — which means what in English? Can’t you post the actual long number so we ignoramuses can compare it visually to 4,294,967,296? Thanks!

  4. r

    economically, NAT is efficient. It is all part of the management & price control of the supply of IP addresses.

  5. Jim

    Paul – 2^128 = 340,282,366,920,938,463,463,374,607,431,768,211,456.

  6. Nick

    3.402 * 10^38 is approx 3 follow by 38 0´s. You can add all the 0’s if you like.

  7. Paul O' Sullivan

    odd numbers are reserved for testing. also, IPv5 wasn’t developed enough for a long term solution.

  8. fredneedle

    The big number is…………….
    And that’s a very big number and can become meaningless which is why it’s written as 3.402 × 1038 The second half of the number, 1038 is supposed to read 10 to the power of 38 but fonts are tricky little beggars. I looked it up on another web site and they estimate that every person on the planet could have 2×1095 (or 2 times 10 to the power of 95) allocated to them. That should be enough, at least for now.
    Don’t sue me if my maths is wrong. I’m trying to get my head round this as much as you are and I’m getting my data from other websites in the hope that it is accurate and helps all of us to have a better understanding.

  9. JK

    This is an interesting article, but I am not clear whether there is any hardware change i.e. in LAN card/wiring fittings etc

  10. dennishobbs

    O.K didnt know you I.T. guys need a lesson of a different class,Real Estate man, you wanna buy real things (where do you think your preciuos packets go)

  11. Carl

    I’ve often wondered this myself. Hopefully more support comes for ipv6 in the future.. It’s kind of better :)

    @ dennishobbs: ..what?

  12. Daniel

    Here is another way of putting that number.

    Just over 340 Undecillion

  13. Wolf

    I bet by the time ISP’s stop bragging their collective behinds and screaming about costs, we are going to need something better than IPv6. Get ready for the days of dial-up again, because unless they start ramping out firmware updates and upgrades, replacing older equipment and cables, we are going to have connection drops like when dial-up was the king. No more streaming anything.

  14. Jimbo

    @Paul–In the vernacular, “3.402 × 1038” = WTF!

  15. Wayne Riker

    China has a larger population than IPv4 has addreses. IPv4 addresses where sold out over a year ago. The only way to get one is to buy it from someone else, Like MS did with Nortel. Using IPv6 you could address every cell in ones own body, could be useful in genetic based cures. Heart patients may have IP enabled heart monitors already, each one needs a unique IP address. Automobiles that can negotiate routes with their GPS and other automobiles will need their own IP address. Every cell phone needs a unique address to function. Pretty soon issues of a small home network will be the least of the Internet’s concern. The change will happen.

  16. stan

    oh no!..oh me, oh my!!…take your loved ones to higher ground !!

  17. pbug56

    For the life of me I don’t understand why ISP’s are not dealing with this. Mine barely accepts that someday they might have to do something!

  18. spike

    @Cory: It makes it easier to host stuff without having to set up a bunch of port forwarding. Also, better connectivity as all ports between addresses can be used, enabling you to use more services easily, etc.

    @JK: Nope, but companies would certainly like to sell you new equipment :) As stated in the article, it could be accomplished with firmware updates, etc.

    @Wolf: IPv6 doesn’t really have anything to do with network speeds, except that it makes more efficient use of it! But connection drops, etc., that you are talking about would never be the fault of IPv6 “not being good enough”. The blame goes to the hardware and network.

    One thing a bit confusing about this article is that in some ways it insinuates that IPv6 implementation is mostly complete. In fact, only a very small percentage of websites are IPv6 enabled (configured with AAAA DNS records). This is why ISP’s in the main are not treating this with urgency. In fact, I just had an ISP sales rep quote me on service; I asked him about their IPv6 support, and he didn’t even recognize the term. Pitiful.

  19. Brad

    Tis a bit of an overkill. If it took a dozen years to require 4billion address, and now we all have one,, Let’s say that we all now want 2 and one for later on. Then allow for gradual expansion over the next 10 years, another 4 billion,, that sort of adds up to 32 odd billion. What the hell do you do with the other 28 digits to the left of the 32 billion, in that big number mentioned above,, and of course those digits to the left are very more significant than those to the right.. Since as there is enough , I want 4 ip addresses, oh hell , I think there cheep ,, give me 5 please….Microsoft is going to be sorry it stocked up in advance. That 3.042 bignumber flooding the market is going to make them 2 c each,, I’m going to sell my shares in MS!

  20. Alex


    Can someone to explain me how to have both versions of IP? I have only IPv4.

  21. Brodiemac

    Let’s put IPv6 into perspective shall we?

    Roughly 50 octillion (50,000,000,000,000,000,000,000,000,000) addresses per person alive on Earth today

    61,977,889,628,116,596,793,421 IPv6 addresses per square foot of the earth’s surface.

  22. Lee Thompson

    Actually doing servers behind double (or more) NATs *is* possible. It’s tricky and certainly not fun but you can do it.

  23. Lee Thompson

    There are a number of problems (still) with IPv6 adoption:

    1. A lot of client and server network software still only supports IPv4
    2. Most home routers only support IPv4
    3. Most ISPs only support IPv4, especially the smaller ones. (For example, my ADSL and WiMAX ISPs both are IPv4 only with no plans to add IPv6.)
    4. IPv6’s downside is it’s more difficult to firewall. (Granted that’s partially due to #2).
    5. IPv6 addresses are rather unwieldy and it can be difficult to set up IPv6 DHCP and DNS services even when it’s supported.
    6. With the evolution of the IPv4 NAT technology (especially with the UPnP port redirection stuff), most home users (and even some businesses) don’t really *need* IPv6. In addition, NAT provides a ‘soft firewall’ of it’s own just due to the way it works. This all makes IPv6 a tough sell if you already have your IPv4 static address.
    7. If something magic happened resolving issues #1-6 and IPv4 was a thing of the past, there’s a new privacy issue. If we all have routable, individual IPv6 addresses we lose privacy and become much easier to track. (There are privacy options as part of the IPv6 protocol but it remains to be seen how well implemented those options are and how well they will work in actual practice.)

    @Sandeep, IPv5 was used by the experimental Internet Stream Protocol (although never actually called IPv5 it used protocol #5). Pretty much not seen since 1995.

  24. Lee Thompson


    If you’re running a reasonably modern OS (Windows 7, Mac OS X, Ubuntu, etc) you probably have IPv6 installed on your computer (or can install it easily). The tricky part is your ISP would need to support it too and that has been very slow going.

    If you REALLY want IPv6 *now* you can set up a IPv6 tunnel (Hurricane Electric and others are giving them away for free). If you do this, make sure you set up a firewall on your PC for it (the tunnel will bypass any NAT/firewall you already have and your OS firewall will need to support IPv6 specifically).

  25. Lee Thompson


    Probably a number of reasons.

    1) The ISP may already have plenty of IPv4 addresses for itself and it’s customers to use.
    2) There may be hardware/software issues where some of their equipment does not support IPv6.
    3) They may not want to spend the money to train up network engineer & IT staff on IPv6 (which is a very different animal than IPv4).

    Just guessing.

  26. bite me

    Good thing I kept my ol’ Smith Carona.

  27. slomem

    How do you ping a 128 bit IP address ?

  28. spike

    @Lee Thompson: As far as problems with IPv6- your numbers 1-3 aren’t problems with the protocol itself, and will have to go away once IPv4 runs out (if ISPs and home network device manufacturers want to stay in business) . As far as the rest of the points, IPv6 is actually more flexible, efficient, and structured (one control protocol versus three, etc.), Everyone interested should read up on SLAAC and Neighbor Discovery, as well. Not more difficult than any other protocol; you have to learn it, of course, as with anything else. Also, considering NAT a soft firewall is a false sense of security.
    Additionally, IPv6 has several security functions built into it. Of course, nobody *needs* it, but after IPv4 runs out, it will quickly become the best option, so it’s necessary to be prepared. There is the privacy issue you mentioned, but new interface IDs can be randomly generated to prevent this if desired.

  29. John C


    At the moment manufacturers and suppliers are using RFIDs to track individual items throughout the supply chain from manufacture to end point sale.

    With integrated networking IPv6 will allow every individual item to have its own unique network address to enable communication with the originial manufacturer for updates etc.(just one example).

    Coupled with open standards the possibilities are limitless.

    As someone else said, things like pacemakers and replacement parts could constantly report back to the manufacturer for automatic detection of potential failure.

    It’s OK if you want to do port forwarding with your router as someone said earlier. Most people just want stuff to work.

  30. John C


    I’m sure I read that the number of IPv6 addresses is more than the number of the atoms in the universe.

  31. Rich

    Cory: Because you have a limited number of port numbers. NAT differentiates between computers using port numbers and there are a little over 65,000 of those. You have multiple sites open and multiple applications on your computer, you can easily use 100 ports.

    Sandeep: To avoid confusion with Internet Stream Protocol packets that had IP version 5 in their headers.

    IPv6 is going to be faster, as well, because routers won’t have to calculate checksums for each IP header. IPv6 addresses are a huge pain to type out though.

  32. spike

    @John C: Woah! Astronomers haven’t even discovered the extents of the universe, and never will. The further out they look, the more galaxies they see. There is no way that this is true, although 340 undecillion is a huge number! You may have heard that there are more IPv6 addresses than atoms in the average human body; this is a more common comparison, and is true. The average human body has 7 * 10^27 atoms in it, compared with IPv6’s 3.4 * 10^38 available addresses. For reference, I’ve seen an estimate that the planet earth has 1.33 * 10^50 atoms of mass.

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