max-ncache-ttl
Barry Margolin
barmar at genuity.net
Thu Nov 8 22:18:35 UTC 2001
In article <9seu63$gfb at pub3.rc.vix.com>,
England, Robert <england at northamerica.exchange.agere.com> wrote:
>We seem to be experiencing an steady stream of DNS domains that we are not
>able to locate. A fair amount of these DNS domains are valid domains, they
>resolve on one of my DNS server but not the other?
>For one reason or another at any given time one of our two DNS servers that
>handle all external DNS look-ups caches a negative response.
What's probably happening is that there's disagreement among the
authoritative servers for the domain. The name exists on some servers but
not on the others. If you ask a server in the second group you'll get an
NXDOMAIN error and cache it.
>I have set "max-ncache-ttl" to 900 this seems to have helped, but not
>eliminated the intermittent lookup failure for a valid domain name.
>Is it wise to lower the limit to say 600 or 300? I know doing so will
>increase the load on the servers but is there any other reason why I should
>not do that?
Not only will it increase the load on your servers, but all the other
servers out there due to your increased number of queries.
>One other question, As I stated earlier we have 2 DNS server that handle all
>external DNS lookups. Is there that much latency on the internet that a
>request times out with out being able to find the name on the first try? Or
>are there a lot of DNS domains and or DNS servers that are not configured
>correctly? I sometimes find myself troubleshooting other companies DNS
>issues because it affects our company's ability to get important email
>though to a partner. Any thought would be helpful.
There are lots of domains (especially reverse domains) that aren't
configured correctly.
--
Barry Margolin, barmar at genuity.net
Genuity, Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
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