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 From:  Chris Buechler <cbuechler at gmail dot com>
 Cc:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] DNS not forwarding
 Date:  Wed, 25 Jan 2006 01:15:00 -0500
On 1/25/06, Lee Sharp <leesharp at hal dash pc dot org> wrote:
> You see, all OS's have a local DNS cache.  They request a lookup.  The
> m0n0wall forwards the lookup.  It times out.  The m0n0 responds with a
> "lookup failed" and the local OS caches that fail.  If you flush the cache,
> or force a new lookup, it will try again.

I believe dnsmasq (m0n0wall's caching DNS server) will probably also
cache those lookup failures, so then it would affect everything on
your network.

> However, I think the root cause is the
> errors.

I would agree.

> > Aren't the collisions just due to it being a half-duplex wireless
> > connection?

Collisions, yes, errors, no.  The percentage of collisions is
reasonable.  The percentage of errors is definitely not.

Keep in mind that DNS is UDP, so if an error causes a DNS packet to be
lost, you're outta luck.  TCP will still function pretty much normally
with ~1% loss.  It will have a measurable effect on TCP performance,
but one that could go unnoticed unless you're actually measuring.