[Cialug] Cialug Digest, Vol 101, Issue 11

[kristau]

DNS might be a good topic for our Back to Linux Basics presentation series.


On Sat, Sep 21, 2013 at 1:41 PM, Moder John II Lee <jmoder at me.com> wrote:

> Lee, thank you for your explanation.  I think I am beginning to understand.
>
> I don't do a lot of server work, but the systems that I do work on all
> tend to function this way, so you are saying that they all have a split
> horizon DNS setup on them?  Does Microsoft do this natively, where are we
> need to "trick" OSX and Linux systems into doing this?  I apologize for the
> naive questions, but one of the reasons I am doing this is to understand it
> better.
>
> So basically you are saying similar to what Ken did, is that I need to
> find a way to make OSXSLS1 the SOA for the local net, but I may need to use
> something like dnsmasq to trick it to doing so?
>
> I am still having a bit of a disconnect though--  On both boxes I get the
> same results--
>
> When I dig @10.0.1.2 A OSXSLS1.moderetnyre.net. I return the record's
> authority section pointing to OSXSLS1.moderetnyre.net.
>
> When I dig @10.0.1.2 A CentOS1.moderetnyre.net I return the SOA to
> godaddy.
>
> My confusion is that in the zone file on OSXSLS1 I have machine (A)
> records for both CentOS1, and OSXSLS1.  Both record are formatted
> identically, outside their unique names/IPs.
>
> The DNS server on OSXSLS1 is set to accept recursive queries from
> localnets and 10.0.1.0/24.
>
>
> John
>
>
> On Sep 21, 2013, at 8:05 AM, "L. V. Lammert" <lvl at omnitec.net> wrote:
>
> > On Fri, 20 Sep 2013, Moder John II Lee wrote:
> >
> >> What you are saying is without doing a "Split Horizon" DNS on the OSX
> >> box there is no way for me to ping a box on my local network by
> >> hostname?
> >>
> > Not quite; You are 'faking' a DNS entry for a local host, and that local
> > host is not defined in your configured DNS server.
> >
> > When you do a DNS lookup on the OSX box, you get the entry you had in the
> > hosts file -  a local hosts file will override a DNS lookup.
> >
> > When youi lookup the local host from another box, the request is rightly
> > forwarded to the configured DNS server and you get zilch.
> >
> > You need to either supply an 'override' at each machine that will use the
> > local hostname (in /etc/hosts), or configure a DNS server that knows the
> > difference between a local host and a 'real' host.
> >
> >> That just doesn't make sense to me.  The OSX box has an A record for
> >> the CENTOS1 box, why would godaddy need one for me to ping it on my
> >> local network?
> >>
> > Because the OSX box is not configured for normal DNS entries in the local
> > subnet (i.e. split horizon), so an inquiry from *another* machine gets
> > forwarded to the 'real' DNS server.
> >
> >> I understand if I want to reach the box from the outside that godaddy
> >> would need a record, but shouldn't my local DNS be resolved locally when
> >> is has the record, and only be forwarded when the record isn't there?
> >>
> > That works ON the OSX machine as there is an overide configured, but a
> > query from an external machine is treated as a 'real' DNS query and
> > forwarded to the 'real' DNS server.
> >
> > Hence, the reason for the split horizon system, where the DNS server is
> > configured with a different local zone. If you lookup dnsmasq, yoiu can
> > see some more information about how this works.
> >
> >       Lee
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>
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-- 
Tired programmer
Coding late into the night
The core dump follows