Comcast is almost finished with their full rollout of DNSSEC.
We had been having problems with clients internet connections when using Comcast. The symptom we’ve been see is to suddenly lose connectivity due to DNS issues, even though the modem shows it is connected and the link is active.
See this URL for more information:
Comcast is now moved over to these DNS servers nationally
Even though they have rolled this out internally the DHCP from Comcast’s gateways are still pushing out the old DNS info to devices. Manually setting the DNS to the new 75.xx… numbers on you router’s LAN DHCP should correct the problem.
See more info on good DNS fixes from Rob Pegoraro of The Washington Post