Re: how to relocate servers transparently
On June 18, 2004 12:49 am, Nate Duehr wrote:
> No, this isn't right. You must lower the TTL time at a bare minimum 2 *
> (Current TTL) ahead of time. Why? Because nameservers out in the real
> world will not even query your nameservers again until the TTL has
> expired, meaning that if you change it today, the FIRST time another
> nameserver that has already cached your records will ask for it again is
> after the *current* TTL expires. Now take the case where one nameserver
> is a forwarder for another (rare, but there are environments where it's
> needed) and the one behind the forwarder could take up to 2 * TTL to
> come ask for new information.
Can you explain that a little further? If my nameserver caches a record with
TTL 86400, and someone asks for it again an hour later I hand them the record
from my cache using TTL 82800 (not 86400). This is certainly what bind does,
if other caching nameservers do it differently then it's a bug IMHO.
I would be very surprised if it is different when DNS queries are being
forward from one DNS server to another. Or did you mean something else?
Fraser Campbell <email@example.com> http://www.wehave.net/
Georgetown, Ontario, Canada Debian GNU/Linux