Although the Airport Extreme is listed as tested by Comcast, the list entry does not spell out which hardware revision actually works for native IPv6 routing. In addition, Apple is consistently vague on the details of IPv6 support changes with hardware revisions. Here is my experience with implementing native IPv6 (and IPv4) with Comcast Business Internet and a Motorola SB6121.
The Gigabit Ethernet second generation Airport Extreme works fine for tunneling IPv6 using 7.6.1. Native IPv6 routing does not work. The current fifth generation Airport Extreme (MD031LL/A, Model A1408) works for both tunneling and routing. I did not test any intermediate models.
The IPv6 specific configuration notes below assume basic router setup for IPv4 and Comcast connections.
Using Airport Utility 6.1 or newer:
Select the Airport Extreme and click Edit
Select the Internet tab and click Internet Options...
Configure IPv6: Automatically
IPv6 Mode: Native
Check Enable IPv6 Connection Sharing
---If you use Airport Utility 5.6, this last should be similar to Advanced > IPv6 > IPV6 Mode: Router (not tested)
Miscellaneous notes -
Have patience while waiting for Concast supplied IPv6 parameters to appear. I takes a while.
When configuring OS X, remember Configure IPv6: Automatically in the appropriate interface settings. This is enabled in Windows 7 by default.
Thanks go to John Brzozowski and Christopher Tuska from the Comcast IPv6 team for help in understanding the Comcast service environment.
After updating the Airport Utility and Airport Extreme firmware on February 8, 2013, it all still works.
Welcome xz4gb8. Thank you for the post. Your input on your working IPv6 setup is greatly appreciated and will be helpful to the other members of the Comcast Business Forum.
This is a bit sideways, but the 7.6.3 update changed the user interface also for tunnels. And, the upgrade process did not propagate tunnel settings properly. An Ars Technica article shows how to reconfigure tunnel settings: http://arstechnica.com/apple/2013/02/airport-extreme-update-breaks-ipv6-tunnels-but-heres-how-to-fix...
Let me add one additional point. The suggestion for using IPv6 Automatic on OS X clients is okay and the recommended setting provided these are not servers. However, you will not want to use Automatic for any servers, as IPv6 has a privacy feature that causes the IPv6 address to be randomly reassigned in the /64 space by default. For servers, you need to set the configuration to Manual, which will by default populate the address with the correct prefix and the MAC derived host part.
The privacy feature is SLAAC, for those interested in looking it up. This feature is also one of the reasons that you need a /64 space for your network in IPv6.
Windows implements this feature, but I do not know how to override it on Windows.
Update: Airport Extreme 5th Generation with firmware 7.6.4 continues to function excellently without any reconfiguration required.
With respect to OS X Servers and Manual IPv6 configuration:
I note that in the Comcast Business Internet environment where I connect, the Airport Extreme is delegated a prefix for the LAN. Using the Automatic IPv6 setting, any recent OS X system will configure each interface with one IPv6 address composed of the assigned prefix followed by an EUI-64 addressed based on the hardware 48 bit MAC address. This occurs regardless of any privacy addresses. This address remains constant through reboots regardless of changes in any privacy addresses.
- Any IPv6 Privacy address can essentially be ignored.
- Manual IPv6 address configuration in end systems is not necessary.
- No special DNS handling is required except for changes in the IPv6 LAN prefix.
- Any Manual address configuration of any end systems increases management workload and recording requirements, as well as adding additional steps to hardware or software reconfigurations.