DNS pulling BGP routes?

Michael Thomas mike at mtcc.com
Wed Oct 6 22:22:43 UTC 2021

On 10/6/21 2:58 PM, Jon Lewis wrote:
> On Wed, 6 Oct 2021, Michael Thomas wrote:
>> On 10/6/21 2:33 PM, William Herrin wrote:
>>>  On Wed, Oct 6, 2021 at 10:43 AM Michael Thomas <mike at mtcc.com> wrote:
>>>>  So if I understand their post correctly, their DNS servers have the
>>>>  ability to withdraw routes if they determine are sub-optimal (fsvo).
>>>  The servers' IP addresses are anycasted. When one data center
>>>  determines itself to be malfunctioning, it withdraws the routes so
>>>  that users will reach a different data center that is, in theory,
>>>  still functioning.
>> Ah, I was wondering if the anycast part was the relevant bit. But 
>> doesn't it seem odd that it would be intertwined with the DNS 
>> infrastructure?
> People have been anycasting DNS server IPs for years (decades?). So, no.
But it wasn't just their DNS subnets that were pulled, I thought. I'm 
obviously really confused. Anycast to a DNS server makes sense that 
they'd pull out if they couldn't contact the backend. But I thought that 
almost all of their routes to the backend were pulled? That is, the DFZ 
was emptied of FB routes.


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