<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small;color:rgb(0,0,0)">But obviously, no number of local parameters can dictate what happens to DNS resolving beyond your local infrastructure (LAN). Even if there were parameters that "suggest" behaviour to upstream servers, those servers could ignore that. I suspect that full zone file retrieval (or full zone file content retrieval) commands might be the only way to be sure that caching is bypassed.<br> <br></div><div class="gmail_extra"><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><font size="2"><span style="font-family:verdana,sans-serif">Hartmut W Sager - Tel +1-204-339-8331, +1-204-515-1701, +1-204-515-1700, +1-810-471-4600, +1-909-361-6005<br></span></font><br></div></div></div></div></div></div></div></div></div>
<br><div class="gmail_quote">On 7 April 2016 at 07:51, <a href="mailto:wyatt@prairieturtle.ca">wyatt@prairieturtle.ca</a> <span dir="ltr"><<a href="mailto:wyatt@prairieturtle.ca" target="_blank">wyatt@prairieturtle.ca</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="font-family:'Calibri','sans-serif'"><div dir="ltr">
<div dir="ltr">dig has parameters to force cache bypass.</div><div dir="ltr"><br></div><div dir="ltr"><div dir="ltr">Daryl</div></div>
</div><br><div>----- Reply message -----<br>From: "Trevor Cordes" <<a href="mailto:trevor@tecnopolis.ca" target="_blank">trevor@tecnopolis.ca</a>><br>To: "Robert Keizer" <<a href="mailto:robert@keizer.ca" target="_blank">robert@keizer.ca</a>><br>Cc: "Continuation of Round Table discussion" <<a href="mailto:roundtable@muug.mb.ca" target="_blank">roundtable@muug.mb.ca</a>><br>Subject: [RndTbl] programatically determine if DNS is down or blocked?<br>Date: Wed, Apr 6, 2016 15:41</div></div><br><div dir="ltr"><pre style="word-wrap:break-word;white-space:pre-wrap">On 2016-04-06 Robert Keizer wrote:
> Why don't you use dig+grep+sed in bash?
Ya, that's one of the ideas (dig). It looks like dig will
differentiate between named down, vs blocked 53, vs simple invalid
domain.
I'm trying to see if there are other ways also, perhaps ones that don't
require a fork. And the dig will send out real queries to real
servers, but I guess it will be tempered by the cache? I'll have to
test what dig does in the different failure modes when a) resolving a
domain that isn't cached vs b) resolving one that is cached.
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