local_unbound: How to prevent caching of SERVFAIL?

[Niall O'Reilly]

On 29 Jan 2020, at 10:31, wolfgang at lyxys.ka.sub.org wrote:

> using local_unbound on FreeBSD 11.3 I have the problem that an
> occasional SERVFAIL is cached for several minutes (not sure about the
> exact length of time but something like 5 to 15 minutes). Is it possible
> to reduce this to something like 10 seconds?

Browsing the unbound.conf manpage and thinking about what kind of fault
would lead to a SERVFAIL, I get the idea that, if there is a relevant
configuration parameter, it might be either infra-host-ttl or
infra-cache-min-rtt.  The latter, if it helps at all, will likely do so by
addressing a possible underlying cause (upstream timeout) of the SERVFAIL.

But I'm guessing. I'm sure there are people on the
unbound-users at nlnetlabs.nl who can give an authoritative (sic!) answer.

Niall O'Reilly