There may be some operating system out there with picture perfect IPv6 support, but I haven't met it yet. Each has some quirks and some problems. As time goes by, more and more people insist on full-featured IPv6 support that will change. In the meantime though don't be surprised if you run into problems every now and again with IPv6 and say Windows 7. I'm not picking on Windows 7; every operating system will have some troubles until everyone is on board with IPv6.
When you're talking serious network hardware from vendors such as Cisco and Juniper all recent equipment supports IPv6. When it comes to SOHO or consumer-grade switches, routers and Wi-Fi access points (AP)s it's a different story.
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The State of small Network Device IPv6 Support
The quickest way to see what supports IPv6, and what doesn't, is to search on the IPv6 Ready Logo Program Approved List. This searchable Web page, supported by the IPv6 Forum, uses a database of Ipv6-compliant equipment that's passed a testing program. Not every vendor uses their services or submits their hardware for testing. Still, it's the closest thing you'll find today to a one-stop guide to which devices have IPv6 support.
You should also keep in mind though that network vendors use firmware to update, and sometimes change, IPv6 support. For example, Linksys disabled 6to4--an IPv6-to-IPv4 tunneling feature that has some interoperability problems--in the Linksys E4200Wireless-N Router Firmware Update 1.0.01. In other words, equipment with some or no IPv6 support may remove, change, or add it tomorrow with a firmware update.
Or not, as case may be. For example, some Linksys hardware, used to sort of support IPv6 with the unstable 6to4 under the unlikely option of "Vista Premium." One such example was the Linksys WRT610N, a dual 2.4/5GHz Wi-Fi wireless router I've used myself. If you have such a device, update the firmware to drop 6to4. If it's still there and on, follow the advice on the WRT610N: Disable 6to4 page.
Today, Linksys does not offer any SOHO/consumer hardware that supports IPv6. Cisco tells me though that The Linksys E4200 we just launched and Linksys routers [the rest of the E series] that will be launched this year will support iPV6." This will be delivered via a free firmware update. I still don't know if older Linksys hardware will be retrofitted with real IPv6 support.
Netgear supports IPv6 in much of their equipment, but I haven't been able to find an easy way to find out which switch, router, or what have you supports IPv6 or not from their Web site. For now, the only thing I can do is recommend that you take a long, hard look at each prospective device's release notes.
With D-Link, you can at least do a search on IPv6 and get a product list. This network vendor currently supports a wireless router, the DIR-632, and half-a-dozen Gigabit switches.
Curiously, enough Apple's AirPort Extreme and Time Capsule support IPv6. The bad news is that they do it with 6by4 or, the smarter move, you can set IPv6 support up manually.
Buffalo Technology, like Netgear, also supports IPv6 on some of their equipment, but makes it even harder to find out which equipment supports it. Here, you'll actually need to dig into the user manuals to find out what's what. That said, the company has a series of routers--WZR-HP-G300NH, WHR-HP-G300N and WHR-HP-GN-that use the alternative DD-WRT firmware and these do offer some IPv6 support.
To sum up, Windows and Linux both do a reasonable job of supporting IPv6. Mac OS X's support is less well documented and is a little shakier, but it's there too. The real pain-in-the-rump for someone who wants to try IPv6 in their home or small office is that not only does a lot of equipment still not support it, but the network hardware vendors usually make it darn hard to find out what does support IPv6.
Come on Linksys, Netgear, et. al. make it easy for us to buy your goods. Just tell us on a Web page what devices and firmware supports IPv6. It can't be that hard!
In the meantime, if you know of any specific hardware that does support IPv6, why not tell all of us about it in the comments? Thanks.