DNS pulling BGP routes?

Fri Oct 8 17:03:52 UTC 2021

(I'm going to hate myself in the morning, but)

On Fri, Oct 8, 2021 at 10:22 AM Masataka Ohta <
mohta at necom830.hpcl.titech.ac.jp> wrote:

> William Herrin wrote:
>
>
> https://engineering.fb.com/2021/10/05/networking-traffic/outage-details/
>
>     our DNS servers disable those BGP advertisements if they
>     themselves can not speak to our data centers
>
>     The end result was that our DNS servers became unreachable
>     even though they were still operational.
>
> means their DNS servers were serving the zone, even after
> they recognize their zone data were too old, that is, expired.
>
>
that's not what this means. I think Mr. Petach previously described this,
but:
  1) dns server in pop serves some content (ttls aren't important right now)
  2) dns server uses some quagga/gated/bird/etc to announce locally: "Hey,
foo/32 here!"
      (imagine this triggers an 'aggregate route' or 'network statement'
(pick your vendor solution) to appear in the global table)
  3) dns server also 'ping backend server set'
  4) when 3 fails for X period of time 'tell quagga/bird/etc to stop
announcing the /32'

then the local pop no longer sources the aggregate (/24 or /23 or
whatever)... so traffic SHOULD (externally)
flow toward another copy of the /23 or /24 or whatever...

there's not a lot of magic here... and it's not about the zone data really
at all.
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