Network Strategy

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I have a customer that essentially has two networks (3 computers + 1
printer each) in his office.  One of the networks has persistent
internet access, the other, only needs sporadic internet access.  It is
a fixed property of this scenario that these networks must, at times, by
physically separated.

His current hardware nearly does the trick.  The internet ready network
clients are made common by a gateway router than also connects to a
cable modem.  Those machines get their ip address from the DHCP server
in the router.  (DHCP hands out from to

The "other" network is brought to their trough with a switch.  Their ip
addresses are static.  They are determined such that they are in the
same subnet as the internet ready network, but with no chance of
collision.  (Address are in the range of to

Printers are fixed in the range between to,
because I'm using TCP/IP ports and I can't trust the router to hand out
the same address.  The printers do not need internet access, they just
need to be available to whatever local machine is on the common network.

Periodically, I'll need to give the "other" network internet access.
Plugging the switch into the router accomplishes this, as long as the
DNS Server entries in the static TCP/IP configurations point to real

Q1) How much do I have to worry about those DNS servers changing and
making my static setups fail?

Q2) Isn't there some way to tell a client to get the DNS server
addresses from the gateway, if the gateway happens to be there, and not
bitch too much if it isn't?

Q3) Am I all turned around on this--is there a better way to implement
this chimera?

- - - -

Although these question sound suspiciously like software questions, I'd
like to point out that I have had a screwdriver on the desk next to me
while I typed this up.

Re: Network Strategy

Grinder wrote:

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first off what kind of router are you using. with regards to dhcp what is
the lease time for the ip address's. given that if you done the printers
by dhcp you can get the dhcp server to assign the same ip address's
to the printers.

dns servers have nothing to do with issuing ip address all dns does is
assossiate an ip address to a domain name.

Re: Network Strategy

On 2/11/2011 4:05 AM, Darklight wrote:
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It's a WRT54G.  The printers aren't really a problem as I don't care if
they can find a DNS server.

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The TCP/IP settings in Windows XP, seen here: /

...have a dependency.  If I select "Use the following IP address:", ie
Static Addresses, the "Obtain DNS server address automatically:" becomes
disabled and my only option is use static addresses there as well.

I would like it if the the style if ip addressing for a machine truly
was independent of the method of obtaining DNS server addresses.

Re: Network Strategy

On 2/11/2011 7:53 AM, Grinder wrote:
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In your DNS entry for the hard coded devices put your actual router's IP
address in the first entry.  You might also add a second entry if it is
needed to point to an internal DNS server (if you use one) for use when
they are not connected to the above mentioned router.

This will allow the router to choose which DNS server is used based on
either a hard coded entry by you in the router or what ever the ISP has
fed into it from the router's WAN connection.  When not connected to the
router the second DNS entry would get used, if one exists.

Re: Network Strategy

On 2/11/2011 1:44 PM, GlowingBlueMist wrote:
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I'll give that another shot.  It did not seem to work before, but maybe
I just need to give the clients a little time to figure it out.


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