4 ms·

Nope. Comcast is dual-stacking, that means no tunnels and no gateways. This initial deployment is a single IPv6 IP to one physical computer running either Windo

Nope. Comcast is dual-stacking, that means no tunnels and no gateways. This initial deployment is a single IPv6 IP to one physical computer running either Windows Vista, Windows 7 or OS X Lion. It's an initial end-user modem test and will keep the external variables to a minimum.

burgerbrain 15y ago
How do they know that single computer isn't doing DHCP/NAT for other computers? Are they doing nmap OS fingerprinting and banking off the assumption that people using Windows/OSX wouldn't be doing that, but people using Linux might be?
- ghshephard 15y ago
  NAT basically doesn't exist in the IPv6 world. Realize that Comcast is optimizing for the 95% of their customer base that just wants something to work. Clearly their will be another 5% that will always go off the beaten path - and will likely be responsible for their own support.
  - burgerbrain 15y ago
    I understand that. I'm wondering how Comcast would be able to selectively roll this out. How do they know the person who has a single computer connected directly to the modem doesn't have more computers behind it? Since they would currently be using IPv4, I would say NAT is a very real possibility.
    - ghshephard 15y ago
      There are two perspective here. One is what Comcast is prepared to support - and they've identified a minimally useful environment, that allows them to start off slowly, and eliminates as many possible variables from the equation as they can. No /48 routing, (no routers on the CPE at all), no proxying, no RFC 4193, no stateless auto configuration, no 4941 privacy extension. That is from the perspective of Comcast and what they'll support. Then, there is the perspective of what the end user can do (with or without telling comcast) - obviously, in the IPv4 case, you can PAT/NAT to your heart's content, and Comcast will be none the wiser. So - depending on whether you want to stay within the confines of what Comcast is "officially" supporting, or working with the realm of what you know will work - you may or may not want to NAT4 (I personally would have no problems doing it) Which brings us back to the question of IPv6 - I don't think there is any mechanism to allow multiple hosts to hide behind a single IPv6 address, so, from that perspective, the "What will Comcast support" and "What will I do" - turn out to be the same perspective. :-)
      - X-Istence 15y ago
        You can run NAT using IPv6 without issues using OpenBSD's pf firewall for example, so yes, you can "hide" multiple hosts behind a single IPv6 address.
        trout 15y ago
        There aren't any widely deployed standards for NAT66. There are some drafts and ideas, but nothing commercially standard. I'd be hesitant to trust these implementations. You're better off using a firewall than a half-baked IPv6 NAT at this point.
        X-Istence 15y ago
        I was simply pointing out that an implementation exists. Whether it is complete or not I can't speak to because I haven't used it. Although, I do tend to trust the OpenBSD crew when it comes to implementing functioning code.
  - deleted 15y ago
    [deleted]
MrFoof 15y ago
This is correct. More specifically, Comcast will be using 6-to-4. If you're wondering if your router is compatible, Wikipedia does maintain a reasonably up-to-date list of known compatible routers: http://en.wikipedia.org/wiki/Comparison_of_IPv6_support_in_routers http://en.wikipedia.org/wiki/Comparison_of_IPv6_support_in_r... The weak link of Comcast for a while was their lack of not providing IPv4 forwarders on IPv6 DNS servers. Many public DNS servers (including Google DNS) are also in the same boat. On a somewhat unrelated hardware note, Comcast actually supports IPv6 on the Motorola Surfboard 6121, contrary to what their compatibility list suggests. The 6121 is simply a revision of the 6120, and typically they provision 6121s as a 6120 with 6120 firmware.
- wmf 15y ago
  I think 6to4 is over; it's time for native dual stack.

burgerbrain 15y ago

How do they know that single computer isn't doing DHCP/NAT for other computers? Are they doing nmap OS fingerprinting and banking off the assumption that people using Windows/OSX wouldn't be doing that, but people using Linux might be?

ghshephard 15y ago
NAT basically doesn't exist in the IPv6 world. Realize that Comcast is optimizing for the 95% of their customer base that just wants something to work. Clearly their will be another 5% that will always go off the beaten path - and will likely be responsible for their own support.
- burgerbrain 15y ago
  I understand that. I'm wondering how Comcast would be able to selectively roll this out. How do they know the person who has a single computer connected directly to the modem doesn't have more computers behind it? Since they would currently be using IPv4, I would say NAT is a very real possibility.
  - ghshephard 15y ago
    There are two perspective here. One is what Comcast is prepared to support - and they've identified a minimally useful environment, that allows them to start off slowly, and eliminates as many possible variables from the equation as they can. No /48 routing, (no routers on the CPE at all), no proxying, no RFC 4193, no stateless auto configuration, no 4941 privacy extension. That is from the perspective of Comcast and what they'll support. Then, there is the perspective of what the end user can do (with or without telling comcast) - obviously, in the IPv4 case, you can PAT/NAT to your heart's content, and Comcast will be none the wiser. So - depending on whether you want to stay within the confines of what Comcast is "officially" supporting, or working with the realm of what you know will work - you may or may not want to NAT4 (I personally would have no problems doing it) Which brings us back to the question of IPv6 - I don't think there is any mechanism to allow multiple hosts to hide behind a single IPv6 address, so, from that perspective, the "What will Comcast support" and "What will I do" - turn out to be the same perspective. :-)
    - X-Istence 15y ago
      You can run NAT using IPv6 without issues using OpenBSD's pf firewall for example, so yes, you can "hide" multiple hosts behind a single IPv6 address.
      - trout 15y ago
        There aren't any widely deployed standards for NAT66. There are some drafts and ideas, but nothing commercially standard. I'd be hesitant to trust these implementations. You're better off using a firewall than a half-baked IPv6 NAT at this point.
        X-Istence 15y ago
        I was simply pointing out that an implementation exists. Whether it is complete or not I can't speak to because I haven't used it. Although, I do tend to trust the OpenBSD crew when it comes to implementing functioning code.
- deleted 15y ago
  [deleted]

MrFoof 15y ago

This is correct. More specifically, Comcast will be using 6-to-4. If you're wondering if your router is compatible, Wikipedia does maintain a reasonably up-to-date list of known compatible routers: http://en.wikipedia.org/wiki/Comparison_of_IPv6_support_in_routers http://en.wikipedia.org/wiki/Comparison_of_IPv6_support_in_r... The weak link of Comcast for a while was their lack of not providing IPv4 forwarders on IPv6 DNS servers. Many public DNS servers (including Google DNS) are also in the same boat. On a somewhat unrelated hardware note, Comcast actually supports IPv6 on the Motorola Surfboard 6121, contrary to what their compatibility list suggests. The 6121 is simply a revision of the 6120, and typically they provision 6121s as a 6120 with 6120 firmware.

wmf 15y ago
I think 6to4 is over; it's time for native dual stack.