why need cache if has forward-only

[Barry Margolin]

In article <hn6U3.77658$y45.981054 at news4.giganews.com>,
Clayton Tang <ctang at escape.com> wrote:
>Hi,
>
>can someone that a look at this... this is a corp subdomain DNS server.
>
>In my named.boot file I have
>
>forwarders    10.20.30.40 ; corp root dns
>option forward-only
>[....]
>cache     .      named.cache
>
>
>In my named.cache file I have
>
>..    IN    NS    dbna.com.
>dbna.com.   IN   A   10.20.30.40
>
>
>My questions are
>
>1) in general, if I use forward-only, then do I need a cache file? The cache
>file lists root servers that I would query without a forwarder directive or
>if forwarder fails. Since all non-local-domain lookups are only going to the
>forwarders, why do I care where the root servers are?

You don't, but BIND won't operate properly without it.  I think this was
finally fixed in 8.2.2.

>2) in my case, the corp root DNS is my forwarder. So even without a
>"forward-only" option, I don't need the cache file, right?

You still need the cache file for the above reason.

>3) unrelated to the files above.... I know named will cache results for name
>lookups outside of my domain. How do I know how many results have been
>cached, where are they cached, which ones are cached, etc.? Is there a tool
>to examine the cached results?

"ndc dumpdb" will dump all of named's memory into a text file named
/usr/tmp/named_dump.db.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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