The other day, I read a post that Carl Franklin had made on his blog about a new Vista laptop that he had to buy on short notice.  The gist of his post that Vista ran pretty well, but he did tweak some of the settings.

One of the settings that Carl had tweaked was to disable IPv6 on all of the network adapters.  For some reason that jumped out at me.  I posted a comment on his blog asking why he did it.  I’m all for disabling services that are not being used, but I like to know what the reason is behind it. 

I did a quick scan through Google, and initially found many hits for how to disable IPv6 with very little explanation on why you should do it.  Carl responded to my comment that he had heard anecdotal evidence that IPv6 can cause conflicts under Vista.

For me, the decision to disable IPv6 on my Vista boxes boils down to two questions:  Do I need IPv6 functionality?  If I don’t need IPv6, does having IPv6 enabled cause any problems under Vista?  Time to go back to Google and due some more searching.

One bit of trivia:  While I was searching for why you would want to disable IPv6 on Vista, I came across a few articles about how Google owns a large block of IPv6 space that works out to be 7.9 x 1028 IP addresses. That’s a large number, no matter how you slice it.   Why does our Google Overlord need that many addresses?

I’ve seen the badge below displayed on a few sites. 

Pretty scary looking, huh?  There is a real concern with the number of IPv4 addresses being used up.  At the current rate of assignment, we just have a few years left before the all of the addresses have been assigned.  That’s why they came up with IPv6, to provide for a virtually unlimited number of IP addresses.  Even with Google hogging billion and billions of IPv6 addresses, we’ll still more than enough to serve this planets needs for the for seeable future.  Right now, the continued use of NAT allows more users to share the same IP address. 

We are seeing all of the IPv4 addresses being assigned, but that doesn’t mean that they are all being used.  If you look at the global IPv4 allocation list, you’ll see that large chunks of the IPv4 space is in the hands of a small number of companies.  For example, Apple owns all the addresses.  That’s over 16 million distinct, global IP addresses.  What are they doing with all those addresses?  And some people still question the need for IPv6 in the first place. 

But I digress, I think we’ll be safe with just IPv4 addresses for the next few years.  At this point, there are no IPv6 only addresses that I want to visit.  They exist, I just don’t need to visit them.  So the answer to my first question is: No, I don’t need IPv6.

So what about leaving IPv6 enabled in Vista?  What does that cost me?  I read about some reports early in the Vista release with IPv6 issues.  Some of that could be attributed to “version 1.0” network drivers.  I did read some reports of http://localhost not working with IPv6 enabled. 

On an IPv6 enabled box, localhost will evaluate to ::1, not the that we call home.  That is what defined for localhost in %SystemRoot%\system32\drivers\etc\hosts as the IPv6 adddress for localhost.  This apparently causes a problem when testing locally hosted websites.  If you remove (or better yet, just comment out the ::1 entry from the hosts file, that was reported to allow web development to continue using localhost and IPv6 installed.

Klaus Graefensteiner has a pretty good explanation of why this is happening.  As noted elsewhere, he recommends editing the hosts file as the work around. I haven’t done any web development on my Vista box, I can’t verify that this is still an issue.  I’m actually planning on doing some web development work from my home machine in the near future, issues with localhost will pop up pretty much immediately. 

As far as I can tell, the answer to my second question is “maybe”.  If the only issue is the localhost issue, then I’ll address it through editing the hosts file as opposed to disabling IPv6 altogether.

I did see the value of one point that Carl made.  If the service is not being used, then disable it.  It’s not enough of an issue for me, but resources are limited, then you want to pick off the low hanging fruits from the list of running services.  If you do actually want to disable IPv6 in Vista, it’s pretty easy to disable or enable IPv6 support (from numerous sources, this one from TechSupportForum.Com)

  1. Go to Start and type in “ncpa.cpl” (without the quotes) and press Enter
  2. Right click on each network connection and select “Properties”
  3. Remove the checkmark from the box next to “Internet Protocol Version 6 (TCP/IPv6)
  4. Click OK to exit the dialog

Lather, rinse, and repeat for each network connection. IPv6 will still remains active for routing and tunneling.

To complete disable IPv^ in the system, you’ll need to add a registry.  Go to registry and create DWORD parameter “DisabledComponents” in HKLM\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters and set it to a value of 0xff and restart the system.

Just remember one thing, if you disable IPv6, you will not be able to use Windows Meeting Space or any application that relies on the Windows Peer-to-Peer Networking platform or the Teredo transition technology.

Bonus Firefox tip:  You can disable Firefox’s usage of IPv6 with out disabling IPv6 for the rest of the system.

In Firefox, type about:config and then in the filter box type dns. You’ll see an entry named “network.dns.disableIPv6”.  Double-click that line so that it reads True, which will effectively disabled IPv6 for Firefox.  You’ll need to restart Firefox for this change to take effect.