DNS newbie question

[icema...@yahoo.com]

Hello everyone,

I have two DNS servers external to my firewall, running BIND 9.2.2.
Any hostnames that they cannot resolve are being forwarded to my ISP's
DNS servers. My servers have zone data files and I wanted to see if
caching was enabled and, if not, to configure BIND so that it is
enabled. After endless searching on Google, I have heard very bad
things about nscd and BIND not working well together so I want to
reconfigure BIND to continue to resolve hostnames with its own zone
data files, forward requests it cannot handle to the ISP's DNS servers,
AND cache the latter results to cut down on requests made to the ISP's
DNS servers. Many thanks.

[David Botham]

bind-use...@isc.org wrote on 05/10/2005 01:11:51 PM:
> Hello everyone,
>
> I have two DNS servers external to my firewall, running BIND 9.2.2.
> Any hostnames that they cannot resolve are being forwarded to my ISP's
> DNS servers. My servers have zone data files and I wanted to see if
> caching was enabled and, if not, to configure BIND so that it is

BIND caches by default.

Dave...

[Chris]

<icema...@yahoo.com> wrote in message news:d5qruk$nck$1...@sf1.isc.org...

Why use forwarders at all. You have a fully capable DNS server so don't send
recursive queries to your ISP's servers. Let yours do the leg work.

Chris.

[icema...@yahoo.com]

Chris, thanks for the advice. At the same time, at least for my
knowledge, I am very curious about the following:

a)The earlier respondent said that BIND caches by default. How do we
know this, i.e. is there a configuration setting/switch in which this
feature is turned on/off? If so, what is it and in what file is it
stored?

b)Is there a way to see the cache data? How is it stored, e.g. is it
written to a file whose contents are wiped based upon the TTL specified
on the DNS server in question or is it memory-resident and wiped out
after a systemm reboot?

Thanks.

[David Botham]

We know this (that BIND caches by default) because we read the
Administrators Reference Manual (ARM) that comes with BIND. You can get
it at www.isc.org. If you are interested in tuning how the cache is
handled, search for the word "cache" in Chapter 6 of the ARM.

>
> b)Is there a way to see the cache data? How is it stored, e.g. is it

Yes. To see the cache use:

"rndc dumpdb"

The cache will be dumped to the file specified by the "dump-file" option
in named.conf (see the ARM, chapter 6).

> written to a file whose contents are wiped based upon the TTL specified
> on the DNS server in question or is it memory-resident and wiped out
> after a systemm reboot?

Yes, it is stored in RAM and wiped when:
- The system is reboot
- The name server process is stopped
- You flush the cache with "rndc flush [view]"

Yes, as the TTL on RR's in the cache expire, those RR's are removed.

Perhaps you should invest a little time into reading the ARM. You have
some great questions. Most of the answers are in the docs...

hth,

Dave...

>
> Thanks.
>
>

[icema...@yahoo.com]

Thanks for all of your help Dave. :-) I work as a sysadmin and,
whenever I have an issue with which to deal and aspects of it are
unknown to me, I usually not only like to get the fix/quick answer but
also like to go completely "under the hood" to know how all of it
works. BTW, one last question(maybe again indicative of the newbie :-)
), what does the acronym ARM mean? Thanks again.

[David Botham]

bind-use...@isc.org wrote on 05/13/2005 09:34:43 AM:
[clip...]

> > We know this (that BIND caches by default) because we read the
> > Administrators Reference Manual (ARM) that comes with BIND. You can
> get

[clip...]

>
> Thanks for all of your help Dave. :-) I work as a sysadmin and,
> whenever I have an issue with which to deal and aspects of it are
> unknown to me, I usually not only like to get the fix/quick answer but
> also like to go completely "under the hood" to know how all of it
> works. BTW, one last question(maybe again indicative of the newbie :-)
> ), what does the acronym ARM mean? Thanks again.

I think the answer to your last question is in the thread (see above). Did
you read the replies?

Dave...

>
>

[David Botham]

bind-use...@isc.org wrote on 05/13/2005 09:34:43 AM:
[clip...]

>
>

> Thanks for all of your help Dave. :-) I work as a sysadmin and,
> whenever I have an issue with which to deal and aspects of it are
> unknown to me, I usually not only like to get the fix/quick answer but

Yes, we all work as sysadmins of some sort or another. In other words,
responding to this list is probably not in our job descriptions. Our
contributions here are at the leave of those who employ us and for the
betterment of the Internet community. As such, it is considered polite to
exhaust other possible avenues before taxing the kindness of those
providing free support. I think this thread has provided you with many
new avenues to explore.

Thanks,

Dave...