Serial Numbers

[Mark_Andrews at isc.org]

> Hi
> I just want to verify something...
> 
> I am of the understanding that serial numbers are only important between
> authoritive servers and have no real meaning for other dns servers?
> 
> lets say we ahve auth1 and auth2 and remotecache1
> auth1 and 2 are authoritive for a given domain, where remotecache1 is just a
> dns server out in the wilderness somewhere....
> 
> Does remotecache1 look up and compare serial numbers from auth1 or auth2
> when the TTL expires and it needs to refresh its information? Does
> remotecache1 care at all about the serial number? I would think that it
> doesnt care what serial number is in the zone.
> 
> Lets say that the given domain was re-delegated to newauth1 and newauth2.
> They specify a serial number that is lower than the old auth DNS servers had
> in their zone. When the TTL expires, remotecache1 should not care that the
> new auth DNS servers have a ower serial, and should still update from the
> newauth1 and 2by going  through the root servers and find the new auth
> nameserverss and query them for the correct information???
> 
> Any input appreciated..
> 
> Brad

	The cache doesn't care.

	However the old servers really should be made slaves of the
	new servers during the transition.  This is most easily
	achieved by making the old master a slave of the new master.
	For this to work the new serial needs to be greater than
	the old serial.  The old slaves then get the new zone
	contents via the old master.

	You have to turn off the old servers or make them serve the
	new zones to prevent caches staying locked to the old
	servers.

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