On So, 15.11.20 18:25, Chris Adams (linux(a)cmadams.net) wrote:
Once upon a time, Stephen John Smoogen <smooge(a)gmail.com>
said:
> Because a lot of networks use routing tricks to send traffic to particular
> DNS server IP addresses. They may round robin, traffic route, or other
> methods to send you to different DNS servers with the same ip address. Even
> if they are all the same 'model' device, they have different features
> turned on or are at different revisions.. so whatever you have cached is
> wrong.
I'm pretty sure that's considered "their problem"... anycast servers
are
expected to behave the same (or similar enough) in terms of features
supported. Real DNS recursive servers like Unbound and BIND keep info
about particular servers by IP.
We do exactly this.
(It is far from perfect though, for example, quad9's DNS servers you
reach via 9.9.9.9 might have a different feature set whenever you
reach them. Try "dig @9.9.9.9 +nsid heise.de" a bunch of times. It
will sometimes advertise an EDNS dgram size of 512 and sometimes of
1232. Which is quite some discrepancy in configuration. — And
sometimes it returns NSID, and sometimes it doesn't, but I am fine to
ignore that.)
Lennart
--
Lennart Poettering, Berlin