[NZLUG] Friday finking: DNS 'map'

Mark Foster blakjak at blakjak.net
Fri Jan 16 16:06:22 NZDT 2015

dig +trace?

; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> blakjak.net A +trace
;; global options: +cmd
.                       280465  IN      NS b.root-servers.net.
.                       280465  IN      NS g.root-servers.net.
.                       280465  IN      NS e.root-servers.net.
.                       280465  IN      NS j.root-servers.net.
.                       280465  IN      NS d.root-servers.net.
.                       280465  IN      NS i.root-servers.net.
.                       280465  IN      NS a.root-servers.net.
.                       280465  IN      NS c.root-servers.net.
.                       280465  IN      NS l.root-servers.net.
.                       280465  IN      NS f.root-servers.net.
.                       280465  IN      NS m.root-servers.net.
.                       280465  IN      NS h.root-servers.net.
.                       280465  IN      NS k.root-servers.net.
;; Received 496 bytes from in 5041 ms

net.                    172800  IN      NS l.gtld-servers.net.
net.                    172800  IN      NS a.gtld-servers.net.
net.                    172800  IN      NS f.gtld-servers.net.
net.                    172800  IN      NS k.gtld-servers.net.
net.                    172800  IN      NS g.gtld-servers.net.
net.                    172800  IN      NS b.gtld-servers.net.
net.                    172800  IN      NS m.gtld-servers.net.
net.                    172800  IN      NS d.gtld-servers.net.
net.                    172800  IN      NS c.gtld-servers.net.
net.                    172800  IN      NS i.gtld-servers.net.
net.                    172800  IN      NS h.gtld-servers.net.
net.                    172800  IN      NS j.gtld-servers.net.
net.                    172800  IN      NS e.gtld-servers.net.
;; Received 486 bytes from in 2401 ms

blakjak.net.            172800  IN      NS ns2.blakjak.net.
blakjak.net.            172800  IN      NS ns1.blakjak.net.
blakjak.net.            172800  IN      NS ns3.blakjak.net.
;; Received 131 bytes from in 221 ms

blakjak.net.            300     IN      A
blakjak.net.            300     IN      NS ns2.blakjak.net.
blakjak.net.            300     IN      NS ns3.blakjak.net.
blakjak.net.            300     IN      NS ns1.blakjak.net.
;; Received 175 bytes from in 10 ms

blakjak at skyhawk:~$

Assuming you're on DSL you should be directing queries at

a) your DSL router (which receives DNS allocation from your ISP at connect)
b) The recursive DNS servers offered by your ISP
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.

... is this what you mean?


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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