[Cialug] Cialug Digest, Vol 101, Issue 11

[Moder John II Lee]

I'd go to that.


On Sep 21, 2013, at 8:49 AM, kristau <kristau at gmail.com> wrote:

> 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
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