Dynamic DNS
Simon Hobson
shobson0309 at colony.com
Thu Dec 18 09:51:40 UTC 2003
Pascal offredo wrote:
>I'd like the hostname to be unresolvable when the machine is not up.
You cannot do that reliably.
IFF you are using an address from a dynamic pool, AND your client
releases it's lease on shutdown, THEN it will mostly work. But bear
in mind that depending on your DNS setup, the client may still be
resolvable for a short time after it shuts down via slave or caching
servers.
But if the client does not shut down cleanly, or does not release
it's lease on shutdown then the DNS will still not be updated until
the lease expires.
Why is it so essential that the client is not resolvable when shut down ?
As a thought, you could run a DNS server on the client, with a small
zone (child of your main zone) containing only an A record for
itself. In the main zone, make the 'public' name of the client a
CNAME to the name in this child zone. When the client is down,
queries for it's name will fail because the target of the CNAME can
not be resolved. You will also needs to arrange that the A record
does not get cached by the other servers.
It will still result in a delay when other attempt to connect to the
service, but they will get a name not found error instead of just a
connection timeout.
Simon
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Simon Hobson, Technology Specialist
Colony Gift Corporation Limited
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