Wow IPV6 works

You can go to this site  http://ipv6-test.com/ and it will test both ipv4 and ipv6 status as well as speed test.  If the ipv6 fails you need three thing to get it going one  - your isp (comcast in your case) needs to support ipv6, can't image they wouldn't, two - your operation system needs to support it, again all OS since Win7 have it on by default, and third your modem has to have it turned on, t is where the catch is, most do not have it on by default unless you have a newer modem, post 2012 when it went worldwide.  To check pull up your modem page, in your address bar put in "192.168.0.1/" without quotes, this will pull up most modem pages, if it doesn't you'll need to do google to find ut how to get to your modems page.  For mine with centurylink I goto advanced setting, ipv6 wan settings and check enabled, then to ipv6 lan settings and set to stateless.  Once I did that I was up and running.  When given a choice it will always use the ipv6 addresses over the old ipv4, the slow ipv4...lol..if available. then you check the test page again to see if it's working.  Any website using the ipv6 address will work much faster, noticeably faster.