Several readers wrote in to note that the .de domain (Germany), which is operated by DENIC [1], had an unplanned outage earlier that lasted a bit over an hour.
There is no official statement yet, but according to one source [2], a bad zone file was loaded and it took a while to fix.

Currently, .de domains appear to be reachable again.

[1] http://denic.de/ (in German)
[2] http://www.tld.sc/en/

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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
Twitter

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The outage looks like it was from approximately 13:30 to 15:30 local time (CEST)

================= Rob VandenBrink ====================