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IPv6 is now enabled on my network and all devices capable of running IPv6 should be good to go. My Windows 7 and Windows 8 PCs all had global IPv6 addresses without any configuration. My Macbook running MacOS 10.9.5 and my iPhone 4 running iOS 7.0.4 also had global IPv6 addresses without any action on my part.

To verify IPv6 is working, just browse to This website will tell you the global IPv6 address used by your device and verify your IPv6 functionality. As you can see from the screenshot below, the test shows my PC is communicating via IPv6 over the Internet. Notice also that the IPv6 address detected by the IPv6 test site matches the IPv6 address displayed in the ipconfig /all output shown above.

Test IPv6

Test IPv6

Another useful test is to type ping from the command line. Google has enabled IPv6, and since IPv6 is now supported on my network, my PC will use IPv6 when communicating to an IPv6 enabled destination. As you can see from the ping output, I'm getting an IPv6 response from to my ping.

Ping IPv6

Ping IPv6

The above test also illustrates the "intelligence" of IPv6. You don't have to decide when to use IPv6. An IPv6 enabled device will use IPv6 when available and fall back to IPv4 when necessary. In the above example, my PC first did a DNS lookup on and received both IPv6 and IPv4 addresses. You can try this yourself. On an IPv6-enabled system, type nslookup from the command line. As you can see below, the DNS lookup returned both the IPv6 address and IPv4 addresses for

IPv6 and DNS

IPv6 and DNS


As mentioned previously, IPv6 eliminates the need for NAT for IP address conservation. However, NAT's "firewall" provides a measure of security by hiding the IPv4 addresses of LAN devices from the Internet. With global IPv6 addresses, NAT is not needed to share a measly single (temporary) IPv4 address, grudgingly assigned by your ISP; you have 18,446,744,073,709,551,616 addresses! But devices that haven't made the jump to IPv6 will still need your router's NAT to share that single IPv4 WAN IP. IPv6 traffic, on the other hand, will simply be routed.

Without NAT, I wondered whether the LRT224 firewall would provide any protection for devices with IPv6 addresses, so again I reached out to Linksys. Linksys informed me that the LRT224 firewall "by default will block a connection initiated from the WAN side unless access rules allow it." So just because an IPv6 address is "global", doesn't mean it can be freely accessed outside your LAN. Whew!

Further investigation of the LRT224 showed it had a section for both IPv4 and IPv6 in its firewall settings. Below is a screenshot of the IPv6 Access Rules. The default configuration on the LRT224 firewall is the same for both IPv4 and IPv6; all traffic initiated from the WAN blocked by default and all traffic initiated from the LAN allowed. As with IPv4, you can still open ports to a specific device, but that can be tricky, given the lack of DHCP client lists. I'll come back to this in a follow-on piece.

IPv6 Firewall

IPv6 Firewall

Closing Thoughts

Certainly, there are pros and cons to IPv6. On the pro side, IPv6 provides unlimited addresses and resolves the issue with IPv4 address exhaustion. Another value to IPv6 is improved connectivity. NAT can be problematic for protocols like VPN tunnels and VoIP. NAT can cause call connection and call quality problems for VoIP users. NAT can also cause problems if you want to host a server, perhaps for gaming or some other purpose. Having a global IPv6 address on your VoIP device or game server removes NAT from the equation and improves connectivity.

IPv6 also opens up a lot of cool new technologies. Many IPv6 enabled routers support IPv6 technologies such as 6to4 and 6rd. 6to4 allows IPv6 packets to be sent over an IPv4 network. 6to4 can be useful if you're trying to connect to a IPv6 destination and your ISP does not yet support IPv6. 6rd refers to IPv6 rapid deployment and is similar to 6to4, as it also provides a means to transmit IPv6 over an IPv4 network. IPv6 also holds the promise of increased security by supporting IPsec security between IPv6 endpoints.

I think the biggest downside to IPv6 is the lack of information and relative immaturity of the technology. I had the benefit of using a Linksys LRT224 with direct access to Linksys engineering to figure out DHCP-PD. However, the manual for the LRT224 doesn't even mention DHCP-PD. Regarding maturity, IPv6 is not a new technology, but it is still new to ISPs, device manufacturers and customers. IPv6 has a lot more advantages than the few points I've mentioned, but it is going to take some time before those advantages are simplified enough so the majority of us can understand and use them.

My experience shows Time Warner has IPv6 working, at least in my area. Comcast also appears to be relatively far along in its deployment of IPv6. Here's a link to Comcast's IPv6 site and Comcast's list of supported devices.

Once I got IPv6 working, I was surprised at how easy it was to set up...once I knew how. I really only had to enable dual-stack and DHCP-PD. My new dual stack network seems to be just as stable and as fast as it was before I enabled IPv6. For the masses to use IPv6, though, it has to work automatically. As IPv6 deployment becomes more widespread, my guess is devices will have dual-stack and DHCP-PD already enabled, eliminating the need for action from the end user.

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