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ROS DNS-client "ignoring" TTL set by own DNS server

Posted: Sun Aug 11, 2019 1:57 pm
by msatter
When I make a static DNS entry and I look in Cache then I see it counting the TTL down for a few seconds and then it starts counting from the top again.

I have to move the static entries to an external DNS server to have a normal TTL countdown of the given TTL value.

Re: ROS DNS-client "ignoring" TTL set by own DNS server

Posted: Sun Aug 11, 2019 2:22 pm
by pe1chl
Of course when the entry is static, the TTL in cache is meaningless. You can consider it as "blank" or "the configured TTL value".
It would be the same in an external DNS server (in the server itself, not in the cache in the router).

Re: ROS DNS-client "ignoring" TTL set by own DNS server

Posted: Sun Aug 11, 2019 6:23 pm
by Sob
It's just display problem, it's counting down in WinBox, but DNS responses always contain full configured TTL.

Re: ROS DNS-client "ignoring" TTL set by own DNS server

Posted: Sun Aug 11, 2019 9:29 pm
by pe1chl
It appears that he is thinking that the correct behaviour is to count down.
But it isn't. The server that holds the actual information should always return the full TTL, and only caching resolvers should count down to zero and then remove the record.
As the MikroTik DNS service is the actual server for the static DNS records and not a caching resolver, the behavior to always return the same TTL is correct.