Le 19/07/2023 à 19:53, Michael Peddemors a écrit :
Real world is a bit different.. DNS Caching.. While DNS Round Robin is
good enough to distribute loads, it isnt' a very good method for
failover, even with a very short TTL. Many home routers, still insist
on caching results for a long time, no matter what the TTL says, and
of course Windows internal caching etc..
Should not confuse the issue.. call it a 'poor man's load balancer' if
you will, but it more of a last line failover, and during the time it
takes for DNS to retry, and find another active node, an AWFUL lot of
disgruntled customers will be calling ;)
Also so interesting to see some resolvers that don't think of using
the second record, if the first one is down..
You're mixing things : DNS and Mail client behavior. It is a non sense.
A resolver will serve records, It does not use them and do not care of
what is behind the record.
A good client use the lists (of A or AAAA) records to connect to the
server and will iterate on the list if the server behind the record is down.
And DNS caching do it job nothing less, nothing more and is out of the
picture.
Emmanuel.
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