Poor network setups.Follow

Because windows is stupid sometimes (most of the time?), and allowed an incorrect address scheme. Although to be fair, most systems will allow you to enter values which may not work properly. Your understanding of the netmask process is correct. The netmask establishes whether a range of addresses are "local" or "remote". Specifically, a local address is one which your interface can speak to directly. There is no router in between them. Everything else is remote. If the address you're communicating with is within the netmask range of your own address, it'll simply broadcast the signal through the NIC and wait for a response from the other computer. If it is deemed to be non-local, it'll send a connection request to the router/gateway address instead. That router will use it's own tables to figure out how to route the packets from/to the other computer, and enable longer distance communication.


It's usually a good idea to use private net addresses unless you actually own the IP address range in question. I'm not sure why 130.130.130.x is given as an example. It's not a range I would use. That address range appears to belong to a university in Australia, so unless you work at "uow.edu.au", I'd pick other addresses. Anything in the 10.x.x.x or anything in the 192.168.x.x ranges are commonly used for private net addresses and wont get you into any trouble. Of course, all of this assumes that you are setting up a private network and that the systems aren't expected to communicate to anything other than themselves.

Pick a smaller netmask. If you've got a device with a network connection to your lan, and another one to a switch with 3 other systems attached (so they can only speak to eachother and the main system), why use a large netmask? Use 255.255.255.0 in most cases. That gives you 254 addressees in that range. Probably far far more than you actually need. It'll also simplify the work.

Since the factory network (I'm assuming that's your lan) is set up on 10.0.0.x, you're presumably using the one system as a gateway, correct? The Windows boxes on that smaller private network should *not* use the same gateway as the factory network. They don't have a direct network connection to that network, only to the primary system. It should have two interfaces, one on the factory network, and one on the smaller private network (the factory network is also private, so I don't want to confuse the two). The secondary network interface on the first system should perhaps be set to 192.168.0.1, with a netmask of 255.255.255.0. It's primary interface should be the 10.0.0.x address with a 10.0.0.1 gateway (or whatever you're using on the factory floor), and whatever netmask is used on the factory network. The two windows boxes should be set to 192.168.0.2 and .3 respectively, with netmasks of 255.255.255.0, and a gateway of 192.168.0.1 (the secondary interface of the primary machine).

If the primary system is being used as a router, you'll need to configure it that way. This usually involves turning on certain services on the secondary interface. I guess that all depends on whether other systems on the network need to talk to those windows boxes. That wasn't clear. I know that a lot of vendor equipment involves the use of multiple computers, all of which need to talk to eachother, but none of which need to speak to a broader network (except one of them of course). We have tester computers with a private network on each (set up more or less exactly as I just indicated). That interface connects to a small switch, which in turn is connected to a few devices. We can connect handlers, probers, diagnostic equipment, etc and control them through the lan connection. Obviously, we don't want those communicating over the floor network (and that would make it difficult to manage multiple otherwise identical pieces of equipment.


Not sure if this helps you or not.

Edited, Aug 12th 2010 5:58pm by gbaji

Were they actually communicating with that address though? It sounds like right now your entire floor is made up of individual systems and small private networks, none of which talk to each other. As long as the systems only need to communicate with eachother, and they're all on that same bogus 130.130.130.x range, it doesn't really matter what the gateway address is set to. They're never going to try to send any packets to that gateway.

You could always open up a cmd window and attempt to ping the gateway address and see what happens. I'm betting you'll get something like "destination unreachable".



A friend of mine went through that same process at a shop he worked at years ago. It's a nightmare if you're not properly prepped. Make sure you've got a system in place for tracking which system gets which IP address (are you guys setting up some sort of DNS service? That will help tremendously), and have a plan for changing the addresses and then connecting to the larger network. In that order, or bad things will happen...


Don't know how familiar your IT guys are with network dos and don'ts, but a good rule of thumb when setting up a lan is to allocate an address range at the beginning of each subnet for "service" systems (DNS, DHCP, NIS, PDC/BDC, etc). Depending on the size of the subnet, this might be the first 10 or 20 addresses. The thinking being that someone is less likely to accidentally configure some random host to the same IP as a critical service if all those services use a specific range of addresses, and you make sure everyone knows not to use say "numbers lower than 20" when selecting IPs for their hosts.