On Wed, Oct 6, 2021 at 10:44 PM Masataka Ohta <mohta@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. Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/