Maintained by: NLnet Labs

[Unbound-users] Strange TTL of the SOA record for a noexist domain query

Likun Zhang
Mon May 9 13:10:44 CEST 2011


Hi,

Bortzmeyer Sent On Friday, May 06, 2011 9:31 PM


> > When I dig example.com soa, I got the following answer:
> ...
> > example.com.            86400   IN      SOA  NS1.example.com.
> root.example.com. 2010091701 3600 900 604800 3600
> 
> Fresh from the authoritative name server so TTL is the original value.
> 
> > Then I dig noexist.example.com a, I got this:
> ...
> > example.com.            3600    IN      SOA     NS1.example.com.
> root.example.com. 2010091701 3600 900 604800 3600
> 
> "Artificial" value for the TTL, per RFC 2308, section 3. Nothing to do
> with the value Unbound has in its cache.
> 
> > I dig noexist.example.com again, the ttl of the soa record changed:
> ...
> > example.com.            86292   IN      SOA     NS1.example.com.
> root.example.com. 2010091701 3600 900 604800 3600
> 
> Original TTL of the SOA record, minus the 108 seconds elapsed between
> the two tests. Not normal, should be 3600 again.

According section 5 in RFC2308, it should be a bug of unbound, especially when the TTL and minimal of soa are different.
 
Thanks
Likun