Negative Caching

bo63 bo63 at
Thu Nov 3 14:59:47 UTC 2005

Newsgroups: free.comp.dns
From: "bo63" <b... at> - Find messages by this author
Date: 3 Nov 2005 06:44:44 -0800
Local: Thurs, Nov 3 2005 8:44 am
Subject: Negative Caching
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I was wondering if anyone else has had this problem and what they have
done to fix it.

My users get to the Internet via a proxy server.  When they request a
site the proxy server asks my DNS server to resolve for the address.
Every once-in-awhile my DNS does not get an answer back from the
Internet, either via my external DNS (which is my ISP's DNS) or a Root
server within a certain amount of time and my proxy server ends up with

a negative cache.  One of the sites that we try to access has a TTL of
60 seconds so basically my DNS is doing a lookup every minute.  Then my

users cannot access the site for a minimum of 10 minutes.  This causes
major problems for my company.  I read somewhere that there is an issue

with Internet DNS taking long times to resolve but I never could find
any work around.  Does anyone have any suggestions?

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