Private in-house domain

[Paul Lussier]

I don't mean to sound condescending, so I apologize in advance if I
come across that way.  I highly recommend you do some reading on IP
addressing and networking and get a good understanding of the basics.

Whether you realize it or not, you are using a variety of terms
interchangably, which can't be.  This is going to add confusion to the
discussion, slow down your learning curve, result in answers to
questions you didn't ask, and ulimately frustrate everyone :)

"Tech Writer" <TechWtr at handspun.com> writes:

> Thanks for all of the suggestions, so far.  I'm going to look at them more 
> carefully, and see if I can fix this by changing my routing table.
>
> Both replies suggested that I change my internal domain to a 192.168.1.x IP 
> range (to match the Linksys) or change my Linksys router to the 10.25.1.x 
> range (to match my mini-domain).

IP addresses are not domains and domains are not networks.

"Domains" are words.  IP addresses are numbers.  Numbers connote
networks.  Networks/numbers *map* to Domains/words.

This may sound obvious, and maybe you even already know this, but
things will go soooo much easier if you first fundamentally understand
this and second actually use the correct terminology at the right
times.

Utimately, it's irrelevant which numbers you use as long as they all
map to what you actually expect.  And this is where problems occur.
You *expect* one thing, which, in reality, does not *map* correctly,
resulting in confusion and frustration.

>  Actually, I'm aware that either of these will work.  My goal was to
> try NOT to do this.

I'm not sure what exactly you're trying to do or not do at this point.

> So, my goal is to try to find a way to set up a mini-domain of 10.25.1.x 

You mean you want a private network using the 10.25.1.x network?  What
netmask do want on that?  A /24, I'm assuming.

> addresses within a LAN that's already set up with DHCP-assigned 192.168.1.n 
> addresses.
>
> I hope that makes sense.

No, not really :) Are you saying you're trying to convert a network
which is currently using a 192.168.1/24 to using 10.25.1/24?  It
sounds like the biggest problem is that you're trying to solve 2
completely separate problems and conflating them into one to the point
where you don't know what's not working and can't figure out where to
start troubleshooting.

Solve one problem at a time by changing only one variable at a time.

First change your network configuration, get that working.  Then
attack the DNS component.  Remember, DNS is merely a mapping of
numbers to words and vice versa.  If things don't work with only using
the numbers, then using words certainly won't work.

First, configure the DHCP to hand out the correct:
   - IP address
   - netmask
   - gateway
   - broadcast 

for each host.  Then, configure each host for DHCP.  Make sure that
works.  Make sure, using this configuration that all hostname
resolution to the outside world actually works.  Make sure that each
host inside your network can ping each other host at the IP level.  In
other words, from one host, can you, using only IP addresses, ping the
other hosts.  At this point, I would not expect hostname resolution
for internal/local systems to work, unless you have local /etc/hosts
files set up.

Once the underlying network is configured correctly, hack the
/etc/hosts file one one or two hosts.  Make a mapping of your new IP
addresses to the hostnames you want (including the domain portion).

If you can get the /etc/hosts mappings to resolve correctly, it's a
short jump to using DNS (remember, DNS was a replacement for keeping a
monolithic /etc/hosts file).

Whichever system is going to be the DNS server, configure it to use a
static IP address, and make sure that it's using the correct IP
address, netmask, gateway, and broadcast.

Ensure that ifconfig and netstat -rn show what you expect to see.
Your default route should be pointing at the router's IP address.  You
should, at this point, be able to ping the router and beyond (at this
point, using only IP addresses).  Assuming your DNS configuration
hasn't changed, you should even be able to ping things like yahoo.com
and google.com if you're lucky :)

Once all this works, you know the undlying network configuration is
correct and working. *NOW* you can start hacking the DNS
configuration.  Start by setting up the zone files, forward and
reverse. Once those are set up correctly, start up named.  Make sure
the DNS server has itself in the /etc/resolv.conf file, and set the
/etc/nsswitch.conf file is set to use 'dns files' for the 'hosts'
line.

Begin by checking the resolution of hostnames (using the host and/or
nslookup commands) and then try to ping them.  This will show that
name resolution is actually working from the DNS server.

Once this works, manually configure one other host to point at your
new DNS server and make sure resolution works across the network.
Once that goes, flip your test DNS client back to getting it's DNS
config from the DHCP server and go hack the DHCP server to hand out
the the new address of the DNS server you want everything to use.

Now, the one caveat to all this is that if you have *all* of your
hosts pointing at an internal system for DNS resolution, be sure to
configure this DNS server to be a forwarding DNS server with the right
configuration so your resolution of non-local hosts continues to work.
Otherwise, you'll be able to resolve all of *your* hosts, but won't be
able to get anywhere off your local network.
>
>>> ...  I'm not familiar with
>>> CentOS, so I don't know if there's an easy way to do that.
>>>
>
> btw... CentOS is just Red Hat Enterprise Linux, with a different logo.

Yup, and all this is, more or less, completely irrespective of
OS. This is all basic networking.  The fundamental knowledge required
here goes for any OS, Linux, Solaris, Windows, Mac.

I hope this is helpful.  Good luck, and report back with how it goes.
We're all here for more questions when you get stuck :)
-- 
Seeya,
Paul