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ksool
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Joined: 27 May 2006
Posts: 337
Location: Cambridge, MA
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 Posted: Tue Aug 21, 2007 6:45 pm Post subject: Can djbdns cache null responses? |
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I'm using djbdns as a local workstation dns cache and have realized that it doesn't cache null responses.
That is, when an application like conky keeps calling for a reverse lookup of an ip, and djbdns gets a "no such name" response, djbdns won't cache that response, and I can't understand why. I tried searching through the djbdns docs to no avail.
Is it possible to do this, or is this by design?
TIA |
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Monkeh
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| Posted: Tue Aug 21, 2007 7:46 pm Post subject: |
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| Because usually if there's no record, there's no TTL. |
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ksool
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Location: Cambridge, MA
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| Posted: Tue Aug 21, 2007 11:31 pm Post subject: |
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Ok, but it seems silly to me. Every time any user asks for a bad name or unregistered ip, the request has to funnel back to the root servers?
I would think caching an empty response for at least a short time would be reasonable. |
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Monkeh
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| Posted: Wed Aug 22, 2007 7:40 pm Post subject: |
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| krs1ars wrote: | | I would think caching an empty response for at least a short time would be reasonable. |
But wrong. You can set a TTL for NXDOMAIN (acknowledgement of no such domain), but many do not. You always honour the TTL, and if it's not there, you do NOT cache. Incorrect TTL behavior by servers is what causes DNS issues. |
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ksool
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Location: Cambridge, MA
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| Posted: Thu Aug 23, 2007 1:51 am Post subject: |
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| Ok, so then I just need to setup my network's bind server to accommodate TTLS for NXDOMAINS. Done. Thanks. |
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