[Unbound-users] caching in case of unreachable NSes

Michael Tokarev mjt at tls.msk.ru
Tue May 19 08:44:50 UTC 2009

For how long unbound caches failed queries?  For now,
if at the time of query the NSes are unreachable, unbound
remembers that "reply" and returns "SERVFAIL" for that
name for quite some time, even if the nameservers are
now reachable again.  To the extent that I have to
restart it to clear the condition.

Note that the QUERY "result" (or lack thereof) is cached,
not the nameservers.  I.e., if I query another name in the
same domain right when the NS becomes reachable, unbound
will process it just fine.  But the original query is still
replied with SERVFAIL.




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