Dual networks - why can't I get a local private network to work?

I have a number of PC's, for testing and experimentation, along with my workstations and servers. I have one Internet connection which is working just fine on all of them. I want to set up a second, private network (no Internet access) with Gigabit speeds for sharing files and for other operations.

Nearly all my computers have at least on-board 10/100. I have enough Gigabit cards so that I can hook them all into a second Gigabit network. I want to use this second network purely for moving files around and for other high-speed operations, but I want to completely isolate it from the Internet. That means no gateway, no DNS servers, especially those on the Internet. That way, the 10/100 (Internet) network would be TCP/IP *only*, and the Gigabit network could run any protocol I wanted to in order to share files and make connections that might otherwise be hazardous when in the presence of a gateway.

I have used the guide provided here: http://www.wikihow.com/Set-up-a-Private-Network to *try* to set up the private network, to no avail. It simply does not want to function.


Internet Connections
IP: 192.168.0.x (depending on computer)
Gateway: (D-Link router)
DNS servers:, (plus a few others)

Local Network:
IP: 192.168.1.x (depending on computer)

For each computer, I have made sure to hard-code the same last digit for both networks. So, for example, my only Windows workstation would have for its 10/100 (Internet) connection, and for its Gigabit (Private LAN) connection.

All of my IP addresses are logically laid out. 2-5 are my network devices (printers, etc.), 6-10 are my servers, and 11-20 are those machines that are neither network devices nor servers, but still require static IP's. Anything over 20 would only be on the 10/100 (Internet) connection anyhow. Those would be my laptops on the wireless connection from the D-Link router and my other half's Mac.

When I hook everything up, the Internet connection still works fine. But I cannot seem to get any connectivity over the Gigabit network. None. Nada. The cards show a proper connection, the Gigabit switch shows lights for each connection, but I cannot ping or otherwise see any other device from any computer hooked up to the Gigabit network.

My question is why the Internet network works just fine, but the Gigabit network doesn't. Rebooting does nothing. Turning firewalls off (for the Gigabit network) does nothing. I can ping a loopback address, I can even ping the full IP of the machine I am on, I just cannot ping any other machine on that Gigabit network.

9 answers Last reply
More about dual networks local private network work
  1. Anyone? Doesn’t anyone have an answer? All I’m hearing here are the crickets!
  2. are you trying to utilize two routers or just one? and also, do you have your other cards enabled to recognize a network connection thru the device manager?
  3. I have just one router, on the 10/100 network, which is connected to the Internet. The whole point of the Gigabit network is to be completely isolated from the Internet, so it has no router whatsoever, just one big 16 port Gigabit switch. Furthermore, when the IP addresses were hard coded on the Gigabit network, I specifically left out the Gateway address and the DNS addresses because they were functionally useless (there is no gateway on the Gigabit network because there is no router, and therefore there are no DNS servers available).

    As for your device manager statement, it makes no sense. Network cards automatically recognize a network connection when:
    1) They have their proper driver installed
    2) They are connected to a viable network via a network cable

    And I only have one Windows workstation. The rest of my machines which are hooked in are running OpenSUSE and Solaris, others which are waiting to be hooked in (once I know how to get things working) include HaikuOS, Mac OSX 10.6, NetBSD, OpenBSD, FreeBSD, Windows 2008 R2, and Mint.

    What is really frustrating is that I appear to be doing everything exactly as I should. The sites I Have examined for advice all tell me to do the same things, which I have. And yet, I seem to be unable to make any sort of a connection over this private network.
  4. "The rest of my machines which are hooked in are running OpenSUSE and Solaris, others which are waiting to be hooked in (once I know how to get things working) include HaikuOS, Mac OSX 10.6, NetBSD, OpenBSD, FreeBSD, Windows 2008 R2, and Mint. "

    lol, that is one mixed environment, turn one of them into a DHCP server, then set everything else to obtain from the DHCP server. Once you have everything in a scope, start to set up reservations by MAC...
  5. Ideally, yes. That *should* work. However, I switch these machines around and rebuild them on a rather regular basis. There is no one single machine that could act an a DHCP server for any serious length of time.
  6. Sounds like there's no routing between the two networks (physically separate cards). Basically, you have configured each system with 2 IP addresses -- one on 192.168.0.x, and another on 192.169.1.x. But you have not set up any routing or bridging between the networks.

    When you run ping, my guess is that it's using the source IP address of your Internet network, and so you can only ping other IPs on that network.

    What happens when you use the -S option of ping to set the source IP address to use? Can you ping the 192.168.1.x IPs when you set source to be on the same network?
  7. -S doesn't do what you suggest under either Windows XP or OpenSUSE. The closest I got was -I under OpenSUSE, and even though it clearly used the right interface the destination host (my Windows machine) could not be reached.
  8. If you unplug or disable the nic for the .0.x network are you then able to communicate with the gig network? If so then the problem is that windows is using the other network for all network activity because it sets it as the default.
    Take a look here on modifying route tables.
  9. Also take your solaris or linux box and see if there is any traffic on that network using tcpdump (linux) or snoop (solaris)... Your overall logic / configuration should work fine... I'd check routing tables as sturm already suggested, and verify that traffic is on that network. No need for DCHP... what you have <should> work as documented. Sometimes you'll be surprised that your linux / unix boxes may have an issue with their netmasks or something... easiest way sometimes is just to look @ the packets on the wire to see what if anything happens. At a minimum if you try to ping / telnet to a port or whatever from unix / linux you should see the arp request / reply on the wire. Who knows... could even be a bad switch or something.
Ask a new question

Read More

Private Network Internet Connection Networking