NSLOOKUP

  • Thread starter Thread starter Wayne
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W

Wayne

I need to see what my name/mail servers are, but I need to do this from the
Internet side of my firewall, is this possible from within my network side
but getting a result as if I were outside my firewall using nslookup

wayne
 
I need to see what my name/mail servers are, but I
need to do this from the Internet side of my firewall,
is this possible from within my network side but
getting a result as if I were outside my firewall using
nslookup

Yes, the trick is specifying a DNS address as the last
parameter of nslookup (if using it in "batch" mode) or
using the "server" command in interactive mode

As an example, let's say you want to perform a DNS
query to see the MX records of the domain acme.com
and you want to use the external DNS 193.155.207.61
you'll only need to enter the command

nslookup -type=MX acme.com. 193.155.207.61

this will tell nslookup to query the DNS at 193.155.207.61
for all the records of type MX belonging to acme.com, now
if you want to use interactive mode... well, just fire up your
nslookup w/o parameters, just .. nslookup, once you will
see the ">" prompt enter "server 193.155.207.61" (without
the quotes) and your queries will use that DNS server

hope this will be of help

Regards


--

* ObiWan

DNS "fail-safe" for Windows 2000 and 9X clients.
http://ntcanuck.com

Support and discussions forum
http://ntcanuck.com/net/board

408 XP/2000 tweaks and tips
http://ntcanuck.com/tq/Tip_Quarry.htm
 
O> Yes, the trick is specifying a DNS address as the last
O> parameter of nslookup (if using it in "batch" mode) or
O> using the "server" command in interactive mode

We are in the newsgroup for Microsoft DNS server, of course, against which
this trick will always work. But note that this trick is not universally
applicable. It will not produce the desired results if one has "split
horizon" DNS service using either separate databases or tagged database
records. This is because the selection of the DNS database to use or the
database records to use will be made based upon the client IP address, which
will of course be an "internal" IP address. Hence the data retrieved will be
those of the "internal" view of the DNS namespace.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-split-horizon.html>

The simplest way to determine what DNS data the rest of Internet will actually
see, even in such configurations, is to employ the services of one of the
several promiscuous proxy DNS services that various organizations supply to
the whole of Internet.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-obtaining-proxy-service.html>
 
O> Yes, the trick is specifying a DNS address as the last
O> parameter of nslookup (if using it in "batch" mode) or
O> using the "server" command in interactive mode

We are in the newsgroup for Microsoft DNS server, of course,
against which this trick will always work. But note that this trick
is not universally applicable.

Huh ... are you sure ?

http://www.stopspam.org/usenet/mmf/man/nslookup.html

and in any case we were talking about windows...
It will not produce the desired results if one has "split horizon" DNS
service using either separate databases or tagged database records.

Or bind views, but .. if you issue the suggested nslookup command
the DNS server you're querying will see your NATted IP address
so it all depends from how it's configured, this has nothing to do with
DNS imo .. btw I may be wrong; that said, one may also use external
tools to perform all the required DNS checks as an example this site
carries a wealth of DNS related tools http://www.dnsstuff.com

Regards
 
O> Yes, the trick is specifying a DNS address as the last
O> parameter of nslookup (if using it in "batch" mode) or
O> using the "server" command in interactive mode

JdeBP> We are in the newsgroup for Microsoft DNS server, of course,
JdeBP> against which this trick will always work. But note that
JdeBP> this trick is not universally applicable.

O> Huh ... are you sure ?

Yes.

O> http://www.stopspam.org/usenet/mmf/man/nslookup.html

What relevance did you think that that page has ?

O> and in any case we were talking about windows...

Read the first two sentences of what I wrote again.

JdeBP> It will not produce the desired results if one has "split
JdeBP> horizon" DNS service using either separate databases or
JdeBP> tagged database records.

O> Or bind views,

BIND's "views" mechanism _is_ "split horizon" DNS service using
separate databases. Read the web page that I pointed to again.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-split-horizon.html#MultipleDatabases>

O> but .. if you issue the suggested nslookup command the DNS server
O> you're querying will see your NATted IP address

No-one has mentioned NAT except you, just now. There is no reason to
suppose that NAT is involved in any way, and even were NAT involved
there is no reason to suppose that the system hasn't been configured
to present the "internal" view of the DNS namespace to the publically
reachable IP address as well. As I said, the trick is not
universally applicable.

O> one may also use external tools to perform all the required
O> DNS checks [...]

As I said in my post:

JdeBP> The simplest way to determine what DNS data the rest
JdeBP> of Internet will actually see, even in such
JdeBP> configurations, is to employ the services of one of
JdeBP> the several promiscuous proxy DNS services that
JdeBP> various organizations supply to the whole of Internet.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-obtaining-proxy-service.html>
 
O> Huh ... are you sure ?

Yes.

O> http://www.stopspam.org/usenet/mmf/man/nslookup.html

What relevance did you think that that page has ?

hm .. you told me to read .. now it
seems you aren't reading either
O> and in any case we were talking about windows...

Read the first two sentences of what I wrote again.

JdeBP> It will not produce the desired results if one has "split
JdeBP> horizon" DNS service using either separate databases or
JdeBP> tagged database records.

O> Or bind views,

BIND's "views" mechanism _is_ "split horizon" DNS service using
separate databases. Read the web page that I pointed to again.

I *do know* what a split horizon is and what BIND views are; the original
poster asked for a way to use nslookup to query an _external_ DNS and
my answer was exactly to that question, now, if there's something you
don't understand or .. don't want to understand that's not my business at
all

Regards
 
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