Comcast, actually any ISP, should always provide two DNS servers from two different IP networks. When the ISP’s primary DNS is unreachable, the secondary address should be consulted and respond.
However, occasionally, the problem is with the DNS configuration and impacts both servers. One possible longer term fix is to set your router to use the primary of one ISP and for the secondary, use the Primary of another ISP or DNS service.
Google provides a public DNS service at 8.8.8.8 or 8.8.8.4 you might want to configure your router’s secondary DNS to one of these addresses.
The other day we had the natural gas company (NICOR) digging in the neighborhood which was followed up by a visit from some AT&T trucks. Maybe this really is a "local" issue.....
Doubling the DNS servers only doubles the opportunity of sabotage, better to address the problems and stop doing what is causing the sabotage.
These big companies like comcast, verizon, microsoft, and face book think they are safe thru their size, they are just the opposite. their size makes them more vulnerable.