[Unbound-users] negative cachetime
davew at hireahit.com
Tue Mar 10 07:58:30 UTC 2015
On 2015-03-10 00:04, A. Schulze wrote:
> How long I have to wait until unbound forget the NXDOMAIN
> and fetch new data from authoritative server? Could that be controlled
> The SOA-Reord for example.org looks like this:
> example.org. 12967 IN SOA example.org. hostmaster.example.org.
> 1501261358 43200 7200 2419200 86400
Up to 86400 seconds, or 24h in this example.
Originally the final parameter in a SOA record was the minimum TTL, and
doubled as a default TTL, but it's now used to control the time a
NXDOMAIN should be cached, so in your example, it's 24 hours. Note that
RFC 2308 actually limits this to 3 hours.
http://www.zytrax.com/books/dns/apd/rfc2308.txt has all the details, but
http://www.zytrax.com/books/dns/ch8/soa.html gives a quick overview.
I don't believe unbound can control how long a negative cache record
lasts, only the neg-cache-size (in bytes), but I believe that this will
still respect cache-max-ttl as well.
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