Windows 2000 clients not caching dns lookups

[tetranz]

Archived from groups: microsoft.public.win2000.dns (More info?)

Hi all

I wonder if anyone can shed some light on this. I have a laptop and
desktop both running Windows 2000 with the latest updates etc. They
both seem to spend an unreasonable amount of time 'Looking up' hosts
even though it found the same site only 10 minutes ago. This is evident
with using both FireFox and my email client, Forte Agent.

The 'DNS Client' service is running but it seems that there is no local
caching or if there is then it has a very short expiry time.

I haven't gone as far as looking at network packets but it seems to go
out to my ISP's dns server when it does this.

I just feel that it should 'remember' recent lookups a lot better or
longer.

Any advice?

Cheers
Ross

 

[Guest]

Archived from groups: microsoft.public.win2000.dns (More info?)

In news:1112706721.787330.119620@f14g2000cwb.googlegroups.com,
tetranz <synergy56@hotmail.com> commented
Then Kevin replied below:
> Hi all
>
> I wonder if anyone can shed some light on this. I have a
> laptop and desktop both running Windows 2000 with the
> latest updates etc. They both seem to spend an
> unreasonable amount of time 'Looking up' hosts even
> though it found the same site only 10 minutes ago. This
> is evident with using both FireFox and my email client,
> Forte Agent.
>
> The 'DNS Client' service is running but it seems that
> there is no local caching or if there is then it has a
> very short expiry time.
>
> I haven't gone as far as looking at network packets but
> it seems to go out to my ISP's dns server when it does
> this.
>
> I just feel that it should 'remember' recent lookups a
> lot better or longer.

The DNS client cache will only cache the records until the Time to live
expires. The same goes for the DNS server. If the client gets the record
from a DNS server's cache, it will only cache the record for the time
remaining on the Ttl.
ipconfig /displaydns will display the contents of the DNS Client cache. You
will find that some records may only have a Ttl of one minute or less, so
you question is based on a premise that one cannot answer unless one knows
the remaining ttl of the record you say should be cached.
Take for example www.yahoo.com, which is a CNAME with a Ttl of 5 minutes,
but the "A" records that resolve the Cname to an IP address only have a Ttl
of 60 seconds. There are many more examples of this, the point is the
maximum time this name will resolve to an IP address from cache is one
minute.



--
Best regards,
Kevin D4 Dad Goodknecht Sr. [MVP]
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