Now We Are Six: IPv6 support

We’re pleased to announce optional IPv6 support for Web sites hosted with our company (just in time for World IPv6 day next week!).

Most customers shouldn’t use IPv6 yet, and if you don’t know what it is, you can safely ignore this post. But if you’re familiar with IPv6 and interested in adding it to your site, this post explains what you need to know.

What is IPv6?

IPv6 is a new way of making Internet connections.

Most computers on the Internet use “IPv4” connections, which have been the standard for about 30 years. Until recently, “the Internet” mostly just meant “computers with an IPv4 address that are able to make connections to any other computer with an IPv4 address”.

Unfortunately, IPv4 has some problems. The biggest problem is that there are only about 4 billion IPv4 addresses available, which isn’t enough to connect every computer that wants to be on the Internet in the future. Almost all of those 4 billion addresses have been used or reserved.

Internet engineers recognized this problem more than a decade ago and created IPv6, a new standard with many more addresses. There are enough IPv6 addresses to give trillions of them to every person on the planet. (IPv6 has other technical advantages, too.)

IPv6 is slowly being added to existing computers so they can use both IPv4 and IPv6. These computers will have two separate addresses: an IPv4 address that looks like “” and an IPv6 address that looks quite different, such as “2001:db8::1:2:beef”.

When two computers on the Internet both have IPv6 addresses, they can use IPv6 to connect to each other instead of using IPv4. In fact, Internet standards say that two computers with IPv6 addresses should always use IPv6. Eventually, every computer on the Internet will have an IPv6 address and every connection will take place over IPv6. IPv4 won’t be used any more.

That’s the theory, anyway. Unfortunately, adding IPv6 addresses to computers has been a slow process. There’s been no pressing need for it: since everyone on the Internet has an IPv4 address, adding IPv6 doesn’t give much of a visible benefit, and people frankly have better things to do with their time.

That changed in early 2011. IPv4 addresses really are running low now. It’s possible that within a year or two, some people connecting to the Internet won’t have an IPv4 address. They’ll only be able to make IPv6 connections, and if you want these people to be able to connect to your Web site, your site will need an IPv6 address.

We now support IPv6 as an optional feature for our Web hosting customers. It’s something you can turn on, but it’s currently not enabled by default.

Can enabling IPv6 cause problems?

Enabling IPv6 can cause problems. When you enable IPv6, we tell the rest of the Internet that computers should make an IPv6 connection to your site if they’re able to do so.

This doesn’t affect the vast majority of visitors to your site: most people only have IPv4 addresses and will continue to make IPv4 connections. The trouble is that a small number of computers on the Internet (perhaps 0.2%) think they can make IPv6 connections, but due to technical problems on their end, they really can’t. Because there aren’t many IPv6-enabled Web sites on the Internet, these people haven’t yet noticed that they have a general problem with their Internet connection. They just think that a small handful of sites don’t work properly.

If you enable IPv6 for your site, these visitors will see an error message and think your site is “down”. Because of this, you should enable IPv6 on your site only if you can tolerate having a small number of visitors unable to reach you. This is probably not a good idea for an e-commerce site, for example.

By the way, if you’re interested in finding out if your computer has this problem, there’s a Test Your IPv6 site that will check your connection. (Just so it’s clear, that site tests your own cable/DSL/dialup connection, not our servers or your site with us.)

Why would anyone enable IPv6 if it might cause problems?

The number of people with IPv6-only connections will slowly increase over time, and the number of people with broken IPv6 connections will slowly decrease.

Eventually there will be more people on the Internet with IPv6-only connections than people with broken IPv6 connections. Enabling IPv6 for your site will then result in more people being able to reach it without errors, not fewer.

We can’t predict when that day will come, and to some extent it depends on who visits your site. There will probably be more IPv6-only computers in China than in the United States, for example, so if your site is targeted at Chinese visitors, your site might see a benefit before other sites. For now, we’re letting individual site owners choose when and whether to enable IPv6.

What is “World IPv6 Day”?

Because of the problems described above, no large site wants to enable IPv6 before its competitors. For example, if Google enables IPv6, a small number of their visitors won’t be able to connect to Google any more. If those visitors try Yahoo instead and find that it works, they’ll switch to Yahoo and Google will lose lots of money. (Make no mistake: 0.2% of Google’s revenue is a lot of money.)

This problem has made Internet engineers enable IPv6 more slowly than they’d like to. Even though almost everyone agrees that enabling IPv6 on every Web site is a good idea in the long run, nobody wants to go first.

The solution to this is World IPv6 Day. On June 8, 2011 UTC (which is 5:00 PM Pacific time June 7), many of the largest sites on the Internet (including Google and Yahoo) will simultaneously enable IPv6 for 24 hours.

During that period, people using computers with broken IPv6 connections will find that they can’t connect to most large sites. The hope is that they’ll complain to their local network manager or ISP (who can fix it) instead of the people running the sites (who can’t). It’s a sort of “Mutually Assured Destruction” pact — World IPv6 Day will cause problems for a small number of people, but the problems won’t make Google look any worse than Yahoo, for example.

Tiger Technologies is participating in World IPv6 Day by enabling our own main site (but not any other URLs) for IPv6 during that 24 hour period. We encourage our more adventurous hosting customers to do so, too. The more sites that people with broken IPv6 addresses can’t reach that day, the more likely it is that they’ll realize the problem is on their end.

If you want to participate, you can either enable IPv6 support yourself during that period and turn it off afterward (by following the instructions below), or you can contact us at any time before June 7 at 5:00 PM Pacific time and ask that we enable your site only for World IPv6 Day. We’ll handle it for you.

How do I enable IPv6 for my site?

If you enable IPv6, your site on our servers will have an IPv6 address (in addition to the normal IPv4 address). Visitors using computers with an IPv6 address will then try to connect to your site using IPv6 connections.

You can enable IPv6 for your site using the DNS section of our control panel:

  • Login to the “My Account” control panel (having trouble?)
  • Click Domain Name Options
  • Click Edit DNS Zone
  • Scroll down to IPv6 support
  • Follow the instructions to enable IPv6 support

(If you want to disable IPv6 after turning it on, the same screen allows you to disable it.)

Is there anything else I should know?

Here are some technical details for IPv6 experts:

  • We’re providing native, dual-stack IPv6. It’s not 6to4 or another tunneling scheme.
  • All our servers have outgoing IPv6 support. They prefer IPv6 for outgoing connections to other IPv6-enabled sites as detailed in RFC 3484.
  • If you enable IPv6, we allow incoming IPv6 connections on ports 80 and 443 (for Web sites) and on ports 22 and 23 (for ssh and telnet). We don’t currently allow IPv6 connections to any other ports or services.
  • IPv6 is fully supported for SSL sites. Our Apache Web servers will recognize the IPv6 address of your site and choose the correct certificate to present to the browser.
  • Each IPv6 site has a dedicated IPv6 address on our servers, and IPv6 reverse DNS for that address works correctly.
  • Except for during World IPv6 Day, we aren’t yet advertising IPv6 AAAA addresses for any of our own sites. This is because we’re extremely sensitive to the reliability of things like mail service on Update: We now use IPv6 on all our own sites.
  • While we consider IPv6 to be production quality on our end, the reality is that some of your site visitors won’t have reliable IPv6 connections on their end. If you have trouble as a result of enabling IPv6, you’ll probably need to just disable it for now.

As always, don’t hesitate to contact us if you have any questions.


  1. This is great. Until today I had no idea you folks existed, but now I see you’re local and good at what you do.

    Do you have the same/equivalent network performance monitoring in place for IPv6 that you do for IPv4? (If you do have IPv6 connectivity hiccups, will you know as quickly as you will with your IPv4 connectivity?)

    Is your IPv6 connectivity under an equivalent SLA with your upstream(s) to your IPv4 connectivity?

    Is your IPv6 connectivity served by the same or equivalent network hardware as your IPv4 connectivity?



  2. Graham Freeman wrote:

    >Do you have the same/equivalent network performance monitoring in place for IPv6 that
    >you do for IPv4? (If you do have IPv6 connectivity hiccups, will you know as quickly
    >as you will with your IPv4 connectivity?)

    Yep, it’s monitored by the same software (Nagios), in the same offsite data center, from a completely separate source network.

    >Is your IPv6 connectivity under an equivalent SLA with your upstream(s) to your IPv4

    Yes, but only to the extent of problems they control. In practice, problems in the middle of connections (in networks that neither we nor our upstream providers control) still happen far more with IPv6 than with IPv4, and an SLA doesn’t help with that, unfortunately.

    >Is your IPv6 connectivity served by the same or equivalent network hardware as your
    >IPv4 connectivity?

    It is on our end, but a similar problem occurs: you’ll find that in any end-to-end IPv6 connection on the Internet today, many of the routers involved are legacy ones that have hardware acceleration for IPv4 but not IPv6, lowering the peak packets-per-second performance in the worst case.

    None of this is generally a problem: in the 9 months since we first posted this, our IPv6 and IPv4 reliability have been virtually identical,and we expect that to continue. But if you’re running a site where you’re concerned about the reliability and maximum peak performance of IPv4 vs. IPv6, we’d probably recommend steering clear of IPv6 for as long as you can, with any provider. The reality is that the Internet is fragile, and keeps working only because people all over the world with decades of experience are constantly fixing it and poking at it… but IPv6 is still in its infancy compared to IPv4, and the decades of experience just aren’t there yet.