Originally Posted by attorney28
What if I was running a business on this DSL account - the problem has already been there for 24 h now and they have not fixed it... grrrrr

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Consider yourself lucky in that at least they admit an issue. Comcast has been known to go days insisting that it's not a DNS problem and maybe it's your cable modem and maybe you'd like to schedule a maintenance visit (at a minimum cost of something like $49).
Now, I have the Comcast DNS as the primary one, and the level3 DNS as the backup.