DNS pulling BGP routes?

William Herrin bill at herrin.us
Thu Oct 7 17:01:51 UTC 2021

On Thu, Oct 7, 2021 at 9:52 AM Masataka Ohta
<mohta at necom830.hpcl.titech.ac.jp> wrote:
> But, this time, the reality strikes back.

Not really. Or at all. Facebook the external service was down hard as
soon as the cross-datacenter connections all failed. Whether or not
the BGP routes for the external DNS were withdrawn had no impact on
the outage.

Facebook's _internal_ DNS, while not anycasted, followed a similar
logic: if the data center is isolated and their data goes stale, they
stop serving potentially wrong answers. Since the routing failure
isolated all of the data centers, this left no usable _INTERNAL_ DNS
on which more or less everything else depends.

I didn't work for the DNS team when I worked as a production engineer
for Facebook but I worked close enough to understand what happened
from the posted description.

Bill Herrin

William Herrin
bill at herrin.us

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