Nameserver TTL's

[Mark_Andrews at isc.org]

> Hello,
> 
> We all know that the TTL's in DNS don't always take
> effect when we expect them due to web caching and policies
> imposed by different providers, but I am not quite sure how
> the following is happening:
> 
> A domain "etown.com", was recently switched between providers.
> The old providers nameservers were "ns1.methodfive.com" and
> "ns2.methodfive.com" which had TTL values of 2 Days.  The
> new providers nameservers are "jedi.colo.jalan.com" and
> "keats.jalan.com" which has TTL values of 1HR.
> 
> It's been almost 7 days since the changes were put into effect
> on the root nameservers, yet there are still provider nameservers
> out there showing the authoritive nameservers for the domain to be
> the methodfive ones.
> 
> In particular, ns1.ironlight.com, shows that it just reloaded it's
> nameservers and that the TTL for the methodfive servers is again
> near two days.
> 
> How can this be happening?
> Any ideas?
> 
> Thanks,
> Matt
> -- 
> Matthew Marlowe       http://www.jalan.com/   (p) 909.799.3805
> mmarlowe at jalan.com   Jalan Network Services   (f) 909.799.3285
> "Quality Web Hosting, Network, Linux, and Solaris Consulting"
> 
> 
	Make the old servers secondaries or turn them off.  Having two
	sets of servers claiming to be authorative for the one zone
	is never a good idea.

	The correct way to change servers is to make the old servers
	secondaries until the all cached records refering to them
	have timed out then decommission.  Just changing the old master
	to be a slave should cause the new zone contents to transfer
	to all the old secondaries.

	Just changing the delegation is not guaranteed to stop sites
	re-learning old delegations if they are not made secondaries of
	the new contents.

	RFC 1034/1035 has always allowed the set of authorative servers
	to be sent in the authority section regardless of whether the
	answer is authorative or not. 

	Mark
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org