Configuring Absolute minimum TTL in BIND-8.4.7

Hello to the BIND-users list,

I am a newly subscribed member to this list, so kindly forgive any faux pas
that I might make when asking assistance. I have searched through the
mailing list archives for an answer to an issue I am experiencing, but I had
not luck, so please don't flame me in case I am asking something that is
regularly asked here. Please also feel free to point me towards the correct
protocol in case this is a dumb question...

In any case, I have a BIND-8.4.7 server that acts as a secondary from a
MyDNS server. The axfr works just fine, but it seems that Bind ignores the
TTL on records where the TTL is less than 300s (5 minutes). It does not
matter if I set the TTL of a record to something smaller (like 30s) on the
MyDNS server, when BIND axfr's it, it makes that TTL 300s. The only thing I
can suspect is that in the Bind source somewhere, there is a #define that
specifies what the minimum TTL is that Bind will accept. If it axfr's a
value less than this, it overrides it with its minimum.

Now I've tried searching through the Bind source for anything '300' and I
have found some definitions, but unfortunately, I cannot assess whether this
is the setting that I am looking for. Could anyone that has encountered this
(and rectified it), please point me in the right direction on where I can
change this?

Thanks,

Stefan Schoeman
South Africa

In article <e9ij75$1p05$1@sf1.isc.org>,
"Stefan Schoeman" <stefan@internext.co.za> wrote:
[color=blue]
> In any case, I have a BIND-8.4.7 server that acts as a secondary from a
> MyDNS server. The axfr works just fine, but it seems that Bind ignores the
> TTL on records where the TTL is less than 300s (5 minutes). It does not
> matter if I set the TTL of a record to something smaller (like 30s) on the
> MyDNS server, when BIND axfr's it, it makes that TTL 300s. The only thing I
> can suspect is that in the Bind source somewhere, there is a #define that
> specifies what the minimum TTL is that Bind will accept. If it axfr's a
> value less than this, it overrides it with its minimum.[/color]

I've never heard of such behavior from a BIND server. Are you sure it's
not MyDNS that's doing it? Have you done "dig <zone> axfr
@<mydns-server>" to see what it's actually sending?

--
Barry Margolin, [email]barmar@alum.mit.edu[/email]
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

Thank you for your reply Barry,

Yes, axfr from the MyDNS server did show the larger TTL. However, I was
still not convinced that it was not the dig from Bind that caused this, so I
did a tcpdump and analysed with Ethereal. Indeed, the MyDNS server reported
the larger TTL, but only for axfr. A dig query for the specific record
returned the correct TTL for the individual record. It turns out that MyDNS
has a configuration setting to override individual record TTL's with the
minimum TTL for the domain itself which is active by default. Altered this
and now Bind gets the correct axfr response.

Thanks for the help.

Stefan Schoeman
South Africa


----- Original Message ----- >
[color=blue]
> I've never heard of such behavior from a BIND server. Are you sure it's
> not MyDNS that's doing it? Have you done "dig <zone> axfr
> @<mydns-server>" to see what it's actually sending?[/color]