[lug] DNS and a thanks for the DSL info.

rm at mamma.varadinet.de rm at mamma.varadinet.de
Sun Aug 27 10:11:41 MDT 2000

On Sun, Aug 27, 2000 at 11:10:21AM -0400, John Starkey wrote:
> > DNS is subtle and quick to anger.

True, true ...

> Does this mean I will neeed to rely on them to enter my records?? That's
> what I was trying to avoid in the first place. This may be a warped view,
> what I wanted to do was have one entry at register.com for backup. Then
> make mine the primary.

Well, that depends on the size ouf your IP-address range. While the
IP space is numeric, the DNS namespace is a tree-shaped space of
strings. When revers mapping was introduced the clever idea (tm)
of mapping on space onto the other was:

 take the IP-Address as expressed in qaudruples and split it up =>  192  168  2  1

 take away the 'Host' parts

 192 168 2 1  => 192 168 2 (attention: this works only if your netmask uses a 
                            multiple of 8, i.e. is a class A/B/C net)

 reverse these 'strings' and append 'inet-addr.arpa.' to it.
 192 168 2 => '2.168.192.inet-addr.arpa.'

 This is what gets looked up if you look up an IP address.

So, technically speaking one can only set up a SOA for a class A/B/C
network. There are clever workarrounds for this (have a look at the
bind-book) but they all involve some sort of work on the side of the
'owner' of the IP-range you happen to live in.

> I think I may be confused about the purpose of reverse. Is it only for
> entering IP@ instead of alpha-numeric??


> And forward would be for entering
> the alpha-numeric and assigning IP@ within??

Forwarding means: go ask someone else ;-)

> So when I do:
> nslookup 

nslookup can do both: use the resolver (which is a system library, _not_ 
a server!) or directly ask a server. In 'nslookup' you can set the
server that gets asked with: 

 server some.nameserver.com.

> It tells me the localhost addy and the name of the server. But tells me
> the server is returning an error. So how do i start the server?? Maybe
> this is the /usr/sbin/ndc (the resolver??) and named (the server, based on
> the d at the end). I just scrolled down and saw that you state this later,
> but ndc??

depends on the server you want to run. I use bind and start that service
from an init script. But the exact workings of this depend on the distribution
you use.

> > 	search example.com
> > 	nameserver
> So does the "nameserver" have an RR or is this just something
> that resolv knows to look for and where?
> > Now look in /var/log/messages to make sure there aren't any errors:
> > 
> > 	guin:named# tail /var/log/messages
> > 	[...]
> > 	Aug 27 00:10:49 guin named[14366]: reloading nameserver
> > 	Aug 27 00:10:50 guin named[14366]: master zone "example.com" (IN) loaded
> > 	(serial 2000082700)
> > 	Aug 27 00:10:50 guin named[14366]: Forwarding source address is
> > 	[].1223
> > 	Aug 27 00:10:50 guin named[14366]: Ready to answer queries.
> > 	guin:named#
> This is one I never see. Using "restart" I get the [ok] [ok] but never any
> entries in messages.

You might need to set the debuglevel of you bind (named) to a higher level
(by sending a SIGUS1 to the server process).

> > As an experiment, you can set up records for "example.com" just as I did
> > above (example.com is allocated for use as an example).
> So you actually set up these records on your machine?? I'll try them. I've
> used three different books and the HOWTO and tried all the simple examples
> I could find.
> > I don't know why your setup wasn't working, but my first guess is: Did you
> > actually use "serial" in the SOA record, or did you put a real number in
> > those fields?  It should look something like my SOA above.
> No, that was just some shorthand. I remembered the entries but not the
> numbers.


More information about the LUG mailing list