On Tue, Nov 30, 2010 at 11:22:18AM -0500, Richard Pieri wrote:
> On Nov 30, 2010, at 7:28 AM, Cole Tuininga wrote:
> > I'm a bit confused what you're trying to accomplish here.  The only 
> > reason I can imagine for putting your own caching resolver between you 
> > and the ISP resolver is if you wanted to override the records for a 
> > particular zone for some reason.
> 
> You don't put your own resolver between you and the ISP's resolver.
> You bypass the ISP entirely.  That's the point.  

It's *one* point...

> The only reason to rely on the ISP's resolvers is if you are
> unwilling or unable to run your own.  

False.  Typically, ISP's DNS servers get a lot more traffic than one
you run yourself at home, so cached answers for sites that you visit
infrequently tend to stay cached, whereas your home server may need to
do a full look-up every time you visit.  As a result, for infrequently
used sites, your ISP's DNS servers will very often be faster.  It's
not completely inconceivable that, if your personal pipe is small and
busy (just e.g. dial-up), hitting your ISP's DNS servers will take
much less time than your own DNS server to resolve sites.  Using your
ISP's DNS servers may also help you somewhat in situations where the
link between the sites you want to visit is wonky, by at least making
the DNS portion of the connection go smoothly, e.g. if you're using a
service that makes many small connections, and the site uses low TTLs
for HA or load management reasons.  There are clearly advantages in
some situations to using an ISP's busy DNS servers.

You might want to put a resolver between your clients and your ISP's
resolver and configure it to "forward first" in the event your ISP's
resolvers are broken it will do its own lookups.  Another reason to do
this is if you want to run your own DNS inside your home network, but
are otherwise happy with the DNS service provided by your ISP.  You
manage your own zones, and forward everything else to the ISP.  

You may also want to do something like this simply to learn how...

-- 
Derek D. Martin    http://www.pizzashack.org/   GPG Key ID: 0xDFBEAD02
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