I guess it just seems like it would make sense to instead default to the last known address if the DNS server can’t be reached. It’s not like Twitter changes their IP address every 15 minutes; I’m guessing they haven’t changed their IP address in years.

That all makes sense, but what I don’t understand is why, if I am using Google’s DNS service, it still goes down even though they should have those IP addresses saved. Or, like you said when the cable company skips step 2-4, why aren’t they just skipping steps 2-4 right now since they can’t check with Dyn. It seems…