[NZLUG] Friday finking: DNS 'map'
nzlug at etelligence.info
Fri Jan 16 17:28:47 NZDT 2015
Thanks for this, but not quite what I had in mind. Please allow me to
try to explain further:
On 16/01/15 16:06, Mark Foster wrote:
> dig +trace?
=is close but lists (only) RootServers
=similarly +showsearch doesn't, nor +nssearch
(yes, I'd like to think I did?dug my research)
=I'll debate/differ from the following (just a little):
> Assuming you're on DSL you should be directing queries at
> a) your DSL router (which receives DNS allocation from your ISP at connect)
=no. I'm on a sub-net with its own DHCP/DNS and need for local dvc
=the DSL router consolidates a number of sub-nets and connects to the
outside world, as you say. However this to a Telecom svc (not my choice,
no recommendation, no comment...), and we have found that (rare
occasional drop-outs aside) their DNSvc is usually slower than OpenDNS
(despite the round-tripping)!
> b) The recursive DNS servers offered by your ISP
=the more of which there are, the slower will be the response...
(but irrelevant to our discussion)
> c) manually move up the query chain (from the root zone, to the TLD and
> upward from there) and see when the various queries fail.
=exactly - but am seeking something starting from the very 'bottom'!
> ... is this what you mean?
=if you look at a dig report, eg
> ;; Received 131 bytes from 126.96.36.199#53(188.8.131.52) in 221 ms
> blakjak.net. 300 IN A 184.108.40.206
=it tells you the Answer one (apparently) requested = the A record.
=above which it advises that resolution was provided by a particular DNS
=what I would like is something like:
(maybe think traceroute...)
0 127.0.0.1 hosts file - not found - referring to DNS
1 192.168.1.251 - not found - forwarding
2 192.168.1.1 - not found - forwarding
3 220.127.116.11 - success
0 I don't use hosts so would be happy to ignore - here for
'completeness' of the resolution process only
1 = the local sub-net's in-house DNSvr
2 = the local router - per your notes, above
3 possibly including 'the answer', eg ...blakjak.net A 18.104.22.168
The objective is to be able to see the (actual) succession of DNSvrs, to
be sure that one is indeed forwarding to the next (per network design),
that the forwarding-succession?chain includes all of the necessary svrs,
eg the local sub-net - and thereby identifying if any problem is totally
in-house or limited to the sub-net (without resort to sneaker-net).
=clearer than mud?
> On 16/01/2015 3:53 p.m., DL Neil wrote:
>> Is there a tool which will show the DNS/named servers which will be/may
>> be/were consulted to resolve an hostName?
>> I've had some trouble resetting my home/office network after replacing
>> the router and access point(s), and upgrading server software. The most
>> intractable issue was DNS not working for DHCP but working happily for
>> static-IP (and defined DNS) clients...
>> It would have been very useful to be able to sit at a client PC and
>> confirm that it resolved a hostName by first consulting the LAN DNS
>> server, then forwarding (and external) request to the router (not), then
>> (perhaps) an ISP's DNS server, thence OpenDNS, and maybe ...
>> Am envisioning a report somewhat akin to traceroute (which spans/links
>> routers rather than DNS servers), or even an RDBMS EXPLAIN-ing the plan
>> of a complex multi-table SQL query...
>> ...or should I have adopted a different approach?
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