DNS server not refreshing

[Kevin Darcy]

The persistence of DNS information is controlled by the domain master for both
caching (via TTL settings on the records) and authoritative servers (via the
"refresh" parameter in the SOA). If you have a problem with changes not
propagating in a timely fashion, then it's likely to be one or both of those
things.

Another complication, however, is "glue records". These are records held in the
parent domain whenever a nameserver for the child domain is actually in the
domain itself, e.g. if ns.foo.com is a nameserver for foo.com. If you use
ns.foo.com for mail as well as DNS, and change its IP address, then it has to
be changed in *two* places: in the zone itself, and in the glue records.
Failure to change the glue records will cause the old address to be cached
*some* of the time, which can result in intermittent failures.

As for being able to force refreshes of remote nameservers through "nslookup",
my mind simply boggles at the Denial-of-Service implications of such a
"feature"...


- Kevin

Stephen Williams wrote:

> I have been having a problem where other DNS providers around the nation are
> not refreshing the DB files on their servers to new information. Apparently
> it is remaining in their cache for weeks after the changes are made. As an
> example,  a user sending an email has their DNS server direct that email to
> the mail server of the old information that was changed weeks ago.  Does
> anyone know why this is occurring on some servers and if there is a command
> to force a server to refresh/update or update the cache on that server,
> possibly from nslookup????