Laptop with Windows 7 Home Premium I want an ethernet connection by cable to a two port ethernet-to-RS232 interface. I do not want to go through a network for security reasons. Using a network, I can assign a local IP address (192.168.1.10) to the interface. I can talk to the interface through my network (laptop to router by wifi, router to interface by ethernet cable). But when I disable the wifi, and connect the interface directly to the laptop by ethernet cable, I fail, even using a cross-over cable. I understand that Windows 7 Home has restricted networking capabilities - do I have to upgrade to Windows 7 Pro, or is there another configuration? Thank you.

I'm not sure I exactly understand your setup (with the ethernet-RS232 interface). Are you saying that: 1. When wi-fi is enabled, you can connect to the interface (by wireless or cable) (How do you know it's communicating by cable if it's connected by wi-fi?) 2. When wi-fi is disabled you cannot connect to the interface by cable. When you say 'I can talk to the interface through my network', what do you mean? Are you using a web-browser to access the interface? The networking restrictions you refer to are to do with the number of client computers that can connect using SMB. This does not affect your case. The fact that you are using Windows 7 Home Edition is not the issue at all. As a trouble-shooting measure, try turning off Windows Firewall, and see if you can connect to the RS232 interface by cable then.

Setup #1: Laptop using wifi to my wireless router. Interface box also connected to network via ethernet cable to the network router through a switch. I then used my webbrowser to assign a fixed IP address (192.168.1.10 to the interface). I can use the interface using this configuration with my application being developed with vb.net. The application sees two virtual serial ports. The two devices at the other end of the interface require RS232 communications, and I wanted to use only a single cable between the computer and the interface, which is located inside the enclosure of my instrument. Setup#2: Wifi turned off at the laptop. Ethernet cable directly between the serial interface and the laptop. This setup is entirely disconnected from my network. I tried both the standard cable and a cross-over cable, which I understand is required in absence of a switch or router. I cannot find any device at 192.168.1.10, either through my web browser or my application. What settings should I change? Thanks for your patience.jeyoung

This may be a stupid question, but is your laptop set to a static IP address, or to obtain IP address automatically (DHCP)? Because if it's DHCP, it will autoconfigure to an APIPA address (169.254.0.0/16), so you will not be able to communicate with the device on 192.168.1.10. (When connected directly by cross-over cable) A note on that: Some ethernet devices have 'auto cross-over detection' (Automatic MDI/MDI-X capability), so it doen't matter if you use a straight or cross-over cable. But if you're not sure, then use a cross-over cable to be safe. In fact all 1000BaseT devices have this capability. Also note: "Unlike the crossover cable described above, with only pairs 2 and 3 swapped, a 1000BASE-T crossover cable also has pairs 1 and 4 swapped."

The laptop relies on an address assigned by the DHCP on the network router. Should I assign it a fixed IP, e.g, 192.168.1.15? That should work on my network when I am connected to it ( I already have a printer with fixed Ip of 192.168.1.2 and several other computers using DHCP), and should it work with the interface? Can I assume the network mask should be 255.255.255.0?jeyoung

Hi jey2, Yes, that's your problem. You need to assign it a fixed IP address, so that when it's not connected to the router, it keeps this IP address, and does not re-configure to an APIPA address. Assign an address to your laptop that the router is unlikely to assign to other clients. Anything over 50 should be fine. E.G. ipaddress 192.168.1.100, subnet mask 255.255.255.0. Note: If you assign a static address to your laptop, you will also need to enter the DNS server entry manually. This should be set to the IP address of your router. This is in case you want to connect to the internet via the router at some stage.

It sounds like we're making progress. The router IP is 192.168.1.1 The dhcp starts at 192.168.1.100 So I can assign a static IP such as 192.168.1.15 to the laptop. I already have my printer assigned a static address of 192.168.1.2. My serial interface is assigned 192.168.1.10 Inspection of the router setup shows the DNS server as 68.87.72.134 Of course, that is the external connection. Is that the additional entry that I need? Or do I simply use the 192.168.1.1?jeyoung

Hi Jeyoung, No, that is the public DNS address that has been assigned to your router by your ISP. The DNS entry you need to put in the laptop is 192.168.1.1. The NAT in the router will take care of the rest. Sorry my advice about the address ranges was a bit off. It varies from router to router, what their default IP scope is. If DHCP starts at 100, set your laptop to any address lower than that that is not being used by another static device (obviously) :-) Cheers, BT

When I set up the router a couple of years ago, I told it to start DHCP at 100. Then any static IPs would be lower. Thanks so much for the help. jeyoung

I take it it's working now? That's good news! "I love it when a plan comes together"

I'm now switching to the isolated system. (I needed internet access for access to the vb.net help files) To assign the fixed IP to the computer itself, which options? Control Panel>Network and Internet>????? All the options seem to assume the existence of a network. Control Panel > Network and Internet > Network Connections > Local Area Connection Properties Displays Realtek PCIe FE Family Controller. Pressing "Configure" displays "Properties". I can assign a network address 192.168.1.15 What else?jeyoung

What version of Windows are you using?

Windows 7 Home Premiun on an HP 620 Laptopjeyoung

In Control Panel, go to Network and Sharing Center. On the left panel, click "Change adapter settings". Right-click on the Local Area Connection in question, and click Properties. Double-click "Internet Protocol Version 4 (TCP/IPv4). Click use "Use the following IP address" radio button, and enter the static address you want your pc to have. Click on the "Use the following DNS servers" radio button, and enter the private IP address of your router. Click OK, OK, Close etc.

That did the trick. Thanks again for the help. jeyoung

Thanks to all of you for the help last July. Now, I have another question, but related. I now want to install the developed application (not Visual Studio development package) onto a Netbook equipped with "Windows 7 Starter 32 Bit" operating system. Bear in mind that I need to use the 10/100 ethernet connection for private connection to another device as two virtual serial ports, and occasionally WiFi for normal internet connections such as printers. The application is small, so the 1gb RAM limitation should not be an issue. Will the "Starter" version of Win7 interfere with that ethernet connection, or will the setup be the same as earlier? jeyoung