[Pdns-users] negative query caching for a delegated sub domain
aldusj99 at gmail.com
Mon Jun 28 23:19:11 UTC 2010
We are running BIND version 9.7.0 environment with a delegated subdomain
that is powered by pdns authoritative servers, and we have been noticing
negative caching behavior on the subdomain that's unexpected. This may not
be a bug, but rather my lack of understanding of pdns.. so I am hoping that
someone on this forum could help in explaining this behavior. (I've
changed the actual domain names as they are only used in our internal
So we have abc.com that BIND 9.7.0 is authoritative for. And in named.hosts
of (host: bind1.abc.com), we have:
xyz 30 IN NS pdns1.abc.com.
xyz 30 IN NS pdns2.abc.com.
On bind1.abc.com, if you query for a host that doesn't exist, this is dig's
> dig nohost.xyz.abc.com @bind1.abc.com
; <<>> DiG 9.3.5-P1 <<>> nohost.xyz.abc.com @bind1.abc.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 1298
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;nohost.xyz.abc.com. IN A
;; AUTHORITY SECTION:
xyz.abc.com. 10800 IN SOA localhost. admin.abc.com. 1 60 3600
My question is, where is the '10800' coming from? The SOA record on
pdns.abc.com has TTL of '86400'
Also, when I check the cache on bind1.abc.com, by doing: rndc -c rndc.conf
dumpdb -all, I see:
nohost.xyz.abc.com. 10796 \-ANY ;-$NXDOMAIN
; xyz.abc.com. SOA localhost. admin.abc.com. 1 60 3600 604800 3600
Once we actually add 'nohost.xyz.abc.com' A record to the mysql database, it
takes significantly longer than 3600 seconds for the A record to resolve on
We are running pdns-2.9.22 with mysql backend on Linux 2.6.18.
In the 'records' table, the SOA looks like this:
id, name, domain_id, type, content, ttl, prio, change_date,
1, xyz.abc.com, 1, SOA, localhost admin at abc.com 1, 86400, NULL, NULL
In the 'domains' table:
id, master, name, last_check, type, notified_serial, account
1, NULL, xyz.abc.com, NULL, NATIVE, NULL,
I've also set soa-refresh-default to '60' as it was the only place in the
pdns.conf where I saw '10800'. And as you can see from the SOA entry, it
correctly shows 60 for the SOA refresh.
If there are additional information that's needed to solve this puzzle,
please let me know. thanks for all your help.
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