Failure detection to change A records - windows cache

Nicolas Ecarnot nicolas.ecarnot at
Thu Jan 13 09:40:06 UTC 2005

Le 12-01-2005, Nicolas Ecarnot <nicolas.ecarnot at> écrivait :
> Hi,
> I played with round-robin and this is working fine. But this does not
> fit with our need of failure detection.
> I'm looking for a way to test some services availaibility of some
> hosts, to enable or disable A records.
> For example, I set up two ldap servers in our network.
> On our DNS I run some knid of ldap watchdog, and when a ldap server
> fails, the watchdog removes the A record for

Another point on which I have doubts : the windows clients of our
network are sending queries to
First, they asked the DNS, then cached this answer.
In case of failure of the first ldap server, my (not yet written)
detection script updates the A entry and change it to target the backup
ldap server.

But on the next query, the windows clients may not ask the DNS, and
still use the previous IP address stored in their cache...

Am I worrying for good reasons ?

Nicolas Ecarnot

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