DNS pulling BGP routes?

William Herrin bill at herrin.us
Thu Oct 7 11:23:00 UTC 2021

On Wed, Oct 6, 2021 at 10:44 PM Masataka Ohta
<mohta at necom830.hpcl.titech.ac.jp> wrote:
> Jared Mauch wrote:
> > This is quite common to tie an underlying service announcement to BGP
> > announcements in an Anycast or similar environment.
> Yes, that is a commonly seen mistake with anycast.

You don't know what you're talking about. If your anycast node stops
receiving updated data and you can't reach any of the other nodes to
check whether they're online, 99 times out of 100 this means a local
failure of some sort. You withdraw the node's announcement so that you
don't serve bad data to the end user. That's what happened here -
because the facebook backbone was down, the DNS servers stopped
receiving updates and determined their data to be stale. Simply
turning themselves off, instead of withdrawing the routes, would
result in suboptimal performance. And 99 times out of 100, not doing
one or the other would cause rather than prevent an outage.

Bill Herrin

William Herrin
bill at herrin.us

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