Re: shorten cache ttl?

Marten Lehmann <lehmann@cnm.de> wrote:
> Hello,

> I'm running two caching nameservers, one with djbdns (dnscache), one
> with BIND. I noticed two difference from djbdns to BIND:

> 1. A record does not exist for a certain domain/subdomain in the
> authoritative nameserver when caching dns is used to resolve first, but
> does exist before resolving the second time

> Behaviour with djbdns: Entry doesn't exist the first time, but entry
> does exist the second time

> Behaviour with BIND: Entry doesn't exist the first time and doesn't
> exist the second time.

> Bind seems to remember the "I didn't find such a record at the
> authoritative dns" for some time and does not ask the authoritative
> nameserver again the second time, while djbdns does. I guess BIND uses
> sort of TTL, but whats the TTL of a non existing record? But even
> existing entries are cached to long (but maybe according to the TTL of
> the authoritative nameserver). Can I overwrite the TTL of the
> authoritative nameservers at my caching nameserver, so that the records
> expire earlier?

Bind obeys RFC2308 ( Negative Caching of DNS Queries (DNS NCACHE) djdns
ignores it.


> Regards
> Marten


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Peter Håkanson
IPSec Sverige ( At Gothenburg Riverside )
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