Re: Do DNS Servers cache?

Kevin Seyer ( )
Sat, 11 Apr 1998 09:18:18 -0500

Hi Paul,

Yes, DNS servers cache. The length ot time they cache is the Time to Live
(TTL) parameter that you set on your authoritative DNS server. When a user
out in Internetland queries their DNS server for a resolution to your
domain name, their DNS server checks its cache and if it finds your domain
then checks to see if the TTL has expired. If so, then their DNS server
considers the data stale and queries the authoritative DNS server (you) for
updated info.

Consider the performance ramifications before you change this parameter.
The shorter it is the more work your DNS server has to do.

Hope this helps,
Kevin Seyer
Dolphin Communications Inc.
Dallas, TX

At 09:44 AM 4/7/98 -0400, you wrote:
>I've moved a few client websites over to another machine (NT4AS/IIS) on a
>different subnet. I'm responsible for both the Primary and Secondary DNS
>servers (NT4DNS) for these domains.
>I've updated a few IP's on both the primary and secondary DNS's to point to
>the new website locations. It works fine from the machines that use these
>DNSs as their default DNS and I've verified them using nslookup.
>My problem is...
>I've tried bring up the 'new' sites from two other locations and it seems
>they are still pointing to the old IP address. When I went into nslookup (it
>defaulted to their own DNS servers - not mine), it reported the 'old' IP
>Do other DNS servers cache IP's from remote domains? If so, how long can I
>expect before the cache on these services to flush and update themselves?
>Thanks in advance for your time and consideration.
>Paul L.
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