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  1. Is there a way already in place to make use of IPv6 as a routable protocol?
  2. Is it possible to buy private IP addresses for IPv6 yet and if so who sells them?
  3. Would there be any performance advantage or reduction in latency from having a network based on IPv6?
  4. Many software vendors tell you to disable the IPv6 capability of your NIC in order to prevent problems with their software. Does use of IPv6 somehow confuse systems also using IPv4?
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4 Answers

Is there a way already in place to make use of IPV6 as a routable protocol?

Yes, but your network infrastructure has to support it, meaning your Operating System, your router and your ISP. The NIC is irrelevant in this case, you can send IPv6 with a modem or a pigeon.

Is it possible to buy private IP addresses for IPV6 yet and if so who sells them?

Your ISP should sell them, ask them (SuperUser is not a place for shopping recommendations). Many US-based ISP's don't offer IPv6 support and/or addresses to their residential clients. If your ISP does not offer IPv6 addresses, you can still get multiple free IPv6 addresses that map to your existing IPv4 address. A couple of the larger tunnel brokers are Hurricane Electric and SixXS.

Would there be any performance advantage or reduction in latency from having a network based on IPV6?

Not really, although IPv6 has a slightly larger overhead the header to payload ratio is still too small.

Many software vendors tell you to disable the IPV6 capability of your NIC in order to prevent problems with their softwar.

If that is true, disable their software. IPv6 is a standard that anyone who claims their software can make use of the Internet has to support. And as said above you'd have to disable it in your OS.

Does IPV6 use in some way confuse systems also using IPV4?

No, IPv4 and IPv6 use totally different stacks in the operating system and their headers are distinguished by their version number. If there is a node on the network whose software cannot handle IPv6 the packets have to be packed inside an IPv4 packet. But this is something you do not have to worry about.

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Is there a way already in place to make use of IPv6 as a routeable protocol?

Yes. You either need a ISP which supports this or you will need to tunnel. In the past it was rare to get IPv6 via your ISP, but now that IPv4 addresses really start to run out ISPs finally seem to support it.

On the other hand, you might just be lucky with your ISP. Mine started supporting it since late 1998.

Is it possible to buy private IP addresses for IPv6 yet and if so who sells them?

Basically the same as with IPv4 ranges. Ask your ISP to allocate some of them for you.

Note that IPv6 address space is much larger. You probably get a large range allocated for you allowing you to to connect supply just about anything you can think of with an unique IP number.

Would there be any performance advantage or reduction in latency from having a network based on IPv6?

No performance advantage is likely, though it depends on what you compare it with:

  • Plain old simple IPv4 is old. It is often handled in hardware (fast) or in via very optimised software paths (e.g. when using a router). People have had decades to learn how to squeeze ever last bit of performance out of it.
  • Compared to IPv4 with an option header: That would cause IPv4 to be handled in software. I expect IPv4 and IPv6 to be equally fast.
  • IPv4 and NATting. Software will need to do extra work for IPv4, while you do not need NAT for IPv6. IPv6 might actually be faster.

Many software vendors tell you to disable the IPv6 capability of your NIC in order to prevent problems with their software.

Their software is broken.

Does use of IPv6 somehow confuse systems also using IPv4?

No. IPv6 and IPv4 (and other protocols) can happily coexist on the same network, and even on the same NIC.

There have been some problems with wrongly configured networks. E.g. where a DNS would happily return a 'yes, we do have a IPv6 address!' while no service was listening on IPv6. Many systems then gave up after trying the IPv6 address without falling back to IPv4.

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  1. Yes, many ISPs are now enabling native IPv6 service, and even if yours isn't, you can probably get IPv6 service at no extra charge by tunneling IPv6 over IPv4 in one form or another, such as GIF (Generic Interface) tunnels to "tunnel brokers" such Hurricane Electric or SixXS. There are other tunneling solutions as well, such as 6to4, 6rd, and Teredo.

  2. IPv4 and IPv6 addresses (and subnets/prefixes) are allocated, not sold. Yes, you can get huge amounts of IPv6 address space allocated for free from your ISP or from the tunnel brokers I mentioned above.

  3. No, using IPv6 often takes a slight performance hit, because many routers handle IPv6 in software, whereas they handle IPv4 in hardware. I believe this is rapidly improving, however. But since there still aren't many things you can do on the Internet with IPv6, you'll almost never end up using IPv6 anyway, unless it's something where you're setting up both ends (client and server) yourself.

  4. Some older OSes would try to make connections over IPv6 in some cases when they didn't have real working IPv6 connectivity, and you'd have to wait for the doomed-to-fail IPv6 connection attempt to time out before IPv4 would be tried (and succeed). Hopefully no modern OSes have this problem anymore. I know Mac OS X v10.7 Lion and later don't have this problem, but I can't speak for Windows 7/8 or various Linux distros.

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I can answer that for various distributions. Many now allow you to set you what you prefer first. E.g. first IPv4, then if that fails IPv6, or the other way around. –  Hennes Jul 26 '12 at 7:48
    
@Hennes. Hmm, I guess it could still be an issue there, then. OS X tries both simultaneously and keeps whichever one connects first. I believe apps that still use older/deprecated or lower-level networking APIs don't get this creamy goodness, so it could still be an issue on OS X for apps that haven't modernized their API usage. –  Spiff Jul 26 '12 at 8:07
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I've been using IPv6 since 2006, when all there was to see was a dancing turtle*, so I can tell you it is very much live on the Internet today. Major websites such as Google and Facebook are already live with IPv6 and if you have IPv6 connectivity from your ISP then you will already connect to them using IPv6.

June 6, 2012 was designated World IPv6 Launch Day, where ISPs, network equipment manufacturers and web site operators committed to deploy IPv6.

To obtain IPv6 connectivity at home, contact your ISP and ask them when they plan to deploy native dual stack IPv6. If the answer is anything but "We already did" and you still want to experiment with IPv6, you can obtain temporary service from an IPv6 tunnel broker such as SixXS or Hurricane Electric. (I use the former in places I can't yet get native dual stack.)

When you obtain IPv6 service as a residential customer, you typically will be granted a /64 subnet, which provides about 4 billion times the amount of address space of the current IPv4 internet - just for your house. It would be virtually impossible for you to use your entire allocation. Even so, business customers can typically obtain additional addresses; I could have a /48 just for the asking if I had even the slightest reason to get such a block.

A typical business will typically have somewhere between a /48 and a /56 depending on the complexity of their internal network. ISPs will have much larger blocks; US cable ISP Comcast has a /31, for instance, from which it delegates blocks to its IPv6 customers.

Whether you experience improved latency or performance depends in large part on where you connect to and what you do when you connect there. For the most part your performance should be virtually identical, give or take a millisecond or two. I know of a few degenerate cases where my IPv6 route dramatically outperforms my IPv4 route (we're talking 120ms round trip on IPv4 and 90ms on IPv6), but none of the reverse.

As for software telling you to disable IPv6, some antique software may still not support IPv6 or may malfunction when IPv6 is deployed, or even simply on an IPv6-capable computer. This of course is a bug with that software, and the software vendor should provide an update (if they're still even in business, which is questionable if any such software is still doing that in 2012). IPv6 has been an RFC for close to 15 years now, and so there's very little excuse for any current software to lack support for it.

(*The turtle only dances if you connect with IPv6.)

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