IP Address


I’m new to this forum.

Here is the link for the other forum where there are more details: forums.mrplc.com/index.php?showtopic=20640

I plan to use an Allan Bradley MicroLogix1100 for a small project. I had to use the DF1(RS232) to connect and in order to do it I have to use and old PenthiumII(my recent computer doesn’t have any com ports, with the old one I changed the IP of the ML1100). I was unable to connect to the device with the Ethernet driver simply because the network card was set to get automatically and IP Address. I made the changes and now RSLinx and RSLogix can go through with the Ethernet driver. I set it up simply by choosing the IP address and subnet mask, all the other fields were left blank.

I set the ML1100 IP address as: I did it this way because it will eventually end up in the factory and the network is set up that way. The old computer got the IP as:

What I need to do to get my recent computer, that runs on Windowx7 Ultimate, is to do the same as the old one. I used the same procedures. I always end up loosing the connection to the router/internet when I click on OK (details: usually my W7 computer is connected directly to the router, for this experiment I used an extra hub/switch that I connected in between and hooked up the old computer and the ML1100. Both computers can access the internet). Windows7 tries to repair the problem, it takes just a few minutes and I get the message that the DNS server was not properly configured or some thing like that. I made a print screen of the pupup screen with MSPaint and attached it. I currently set up my W7 as French so I don’t know what the correct English words are.

I tried this experiment again and filled the first 3 fields as: IP: Subnet mask: and the other as: This has failed again. My router’s IP Address is:

Can any body help me figure out what need to be set in the fourth and fifth box?

I also remember that my PC motherboard has two LAN ports. Only one is used. I could change the parameters of the other one. I have a cross cable and the ML1100 and PC could be connected directly. Would it be the same way to make the settings for both scenarios?

Thank you.


First off, hope you don’t mind that I moved the topic- the knowledge base is more for people posting solutions to common problems, not asking question. Since this question revolves around networking more than anything, I thought the “networking” forum would be appropriate.

OK, so, you asked what the DNS server boxes should be. There’s 2 ways to figure this out:
Option A) Find out what your other machines are using. On the machine that can access the internet, go to “Start>Run” and run “cmd” (no quotes)- this just gets you to the command line. Then run “ipconfig /all” (again, no quote). Find the adapter with the address you mentioned, and write down what it’s using for its “DNS servers”.
Option B) Find a public DNS server online to use. http://www.opendns.com/ is your best bet. Go there, find the free version, and it will give you some server addresses you can use.


You won’t be able to talk to the PLC and router with that address scheme. 192.168.100.x is on a different network than with the subnet mask you’re using. means that the first 3 numbers must match up to be on the same network. (Don’t try to put them on the same network via changing the subnet masks either - you’re trying to drop the PLC into the existing plant network)

If you want to talk to the PLC set the address to something like:
address: 192.168.100.x, where x is between 3 and 254 (like
subnet mask:
The rest won’t matter - you won’t be able to access the Internet

If you want to talk with the router:
address: 192.168.1.x, where x is between 2 and 254 (like
subnet mask:
default gateway:
DNS: (assigned by ISP). It would work to use any. For example, I remember the UC Davis DNS servers. and

You should be able to access the Internet if the router is configured properly.

Typically, automatically getting IP info from the router (DHCP) will allow you to access the Internet.

If you want to be able to access the PLC and the Internet, do one of the following (I recommend #2):

  1. Change the PLC address to (from
  2. Change the Router’s address to Set the DHCP scope (automatic address range) to something like Have the PC autoassign an address. It should work fine.

[color=#0040FF]First I’m going to reply to Colby,

I was already familiar with the command: ipconfig/all. I didn’t think of taking down all the available information for the LAN card that connects me to the network and internet. This is in the automatic mode.
IPv4: (prefered)
DNS are:;;

I also took down the information from the MicroLogix1100 through the web browser:

Ethernet: 00-0F-73-00-C2-64
IP: (I had set it up through RSLogix)
Default Gateway:

What I did:

I removed the ML1100 from my improvised home network and hooked it directly to my PC through the second LAN with a cross wire. Once the PLC on W7 detected the connection and showed it in the Network window. There I accessed the parameters for the card and made the appropriate changes. I remind you that with this card I don’t need to go on the net.

Here is what I inserted:


I’ve reasons to believe that only the first two boxes needed to be modfied and that the last ones have no impact.

With those changes made I can have RSLogix communicate with the PLC via the Ethernet port. Finally.

Next step is to have Ignition recognize the device and do what I need to do.[/color]

[color=#FFBF00]Now I’m answering Nathan

OH BOY!!! that’s allot of details.

What I understand is that this is what I need to do if I want to connect to the PLC via my improvised home network and still have access to the internet.

There is one thing that I need to point out: I’m new to Ingnition. I work on the project on my own time at home, once I am familiar with crating the Windows and Clients and the SQL ect I will hook this PLC to the network and the assembly line. Currently it is not decided if Ignition will be temporarily installed on a PC or on the factory’s server.

I programmed the ML1100 with an IP address to match the one of another PLC (SLC500/552)that’s on the network. Before I put the ML1100 I will ping the new IP to make shure there are no other PC with it. The network there runs with the 192.168.100.x.

I hope it won’t be to difficult to set it up.

I will definitely need to read a few times your first reply to understand it…
Thank you to both of you.

The IP address has nothing to do with Ignition - that’s windows and networking. To put it simply:

The 3rd digit of the IP addresses need to match for the devices to talk. Your router uses 1 (to provide Internet access) and your PLC uses 100. Those schemes don’t jive. Decide if you want to use 1 or 100 for your PC.

There are lots of work-arounds, but that’s your fundamental issue.

Thanks for the information.