I am trying to verify an inconsistency that I am experiencing with
regards to negative TTL (or if I have simply misunderstood something
here). tinydns is returning the default SOA record TTL on NXDOMAIN queries:
$ dnsq a blah.pbandjelly.org ns.rackspace.com
1 blah.pbandjelly.org:
100 bytes, 1+0+1+0 records, response, authoritative, nxdomain
query: 1 blah.pbandjelly.org
authority: pbandjelly.org 86400 SOA ns.rackspace.com
hostmaster.rackspace.com 2007021615 10800 3600 604800 300
The same query against one of our old BIND servers does provide the
negative TTL:
$ dnsq a blah.pbandjelly.org lbdns1.rackspace.com
1 blah.pbandjelly.org:
100 bytes, 1+0+1+0 records, response, authoritative, nxdomain
query: 1 blah.pbandjelly.org
authority: pbandjelly.org 300 SOA ns.rackspace.com
hostmaster.rackspace.com 2007021615 10800 3600 604800 300
The SOA record for this domain:
Zpbandjelly.org.:ns.rackspace.com.:hostmaster.rackspace.com.:2007021615:10800:3600:604800:300:86400
>From my understanding of RFC 2308, the reply of 86400 is, essentially,
an incorrect answer, and that I should be getting 300 back from the server.
Section 5 - Caching Negative Answers - "As there is no record in the
answer section to which this TTL can be applied, the TTL must be carried
by another method. This is done by including the SOA record from the
zone in the authority section of the reply. When the authoritative
server creates this record its TTL is taken from the minimum of the
SOA.MINIMUM field and SOA's TTL."
I may implement a workaround, setting the default SOA TTL to 300, if you
happen to try the above queries - I am more interested in seeing if your
own servers respond similarly to non-existent hosts. Thanks for your help!
Kind Regards,
Michael Shuler
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