[Cialug] Cialug Digest, Vol 101, Issue 11

[L. V. Lammert]

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