Re: [cobalt-users] propagation..

[Frank Smith <fsmith@xxxxxxxxxxx>]

Last year when we renumbered our server farm we ran into the same problem.
We thought we were smart by setting the TTL and expire times down to one
day a week ahead of time, and down to one hour a couple of days ahaed of time
(and yes we did update serial #s).  Then late on a Friday we changed the DNS 
again and changed IPs on the servers, leaving one on the old subnet to catch
the stragglers.
    Much of the traffic moved within 1 hour as expected, but there were still
hits on the old addresses for several days, most ending after 78 hours.
    Suprisingly (to me at least), the domains ignoring the TTL were not the
joe-bob ISP variety, but the big boys such as UUNet and PSI.  Evidently they
feel they know better and don't have to follow standards, especially if it
involves CPU or bandwidth ( = money).  Obviously their DNS servers are set up
in a non-standard way with fixed TTL and nothing you can do will change it.
Depending on when they last refreshed a domain, your changes could be seen
anywhere from almost immediately up to as late as their fixed TTL.  
     Moral of the story - Plan ahead, and if your traffic is important then
either stack the old and new IPs on the servers for awhile or leave a server
on the old address(es) with a redirect page.

Frank

    
Jeff Lasman wrote:
> 
> At 04:39 PM 2/10/00 -0500, you wrote:
> >While I have your attention, <evil grin>, that TTL of 86400 means that any
> >site should check the DNS after one day for an update?
> 
> Absolutely.
> 
> >If so, and that is
> >the TTL that was set on all my domains, which is why I can't understand why
> >@Home's DNS servers were caching the info for 5 days when the root
> >nameservers had the update already.
> 
> My question exactly, already stated in this very thread, I think <smile>.
> 

-- 
Frank Smith                                          fsmith@xxxxxxxxxxx
Systems Administrator                               Voice: 512-374-4673
Hoover's Online                                       Fax: 512-374-4501