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From Matus UHLAR - fantomas <>
Subject Re: TTL and DNSBLs (was Re: Why run your own DNS server?)
Date Thu, 07 Jul 2011 09:50:44 GMT
>> > My experiments on real mail servers show that DNS caching is quite
>> > ineffective for DNSBLs (at least for typical ones like Spamhaus that
>> > use a short TTL on the order of 15-30 minutes.)

>On Tue, 5 Jul 2011 12:20:18 +0200
>Michelle Konzack <> wrote:
>> Is the TTL set global or are the TTLs set by IP?

On 05.07.11 16:37, David F. Skoll wrote:
>My simulation assumed the same TTL for all addresses.  But that's not
>relevant to cache effectiveness since most IPs are not listed in a
>DNSBL (and you end up using the negative-cache-TTL.)

Negative caching can be effective or in this case even 
ineffective too, can't it?

>> I have a local bind9 which implement my private list and it set the
>> TTL per target which is quiet effectiv
>If most targets are not listed, per-IP TTLs don't matter.

They do, if the targets repeat.

Matus UHLAR - fantomas, ;
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