Networking – Inserting a non-Internet LAN cable breaks wifi

This is almost certainly due to a security policy. Windows is perfectly capable of operating wired and wireless connection simultaneously but most corporate systems impose a policy whereby, if the wire is connected, the wireless will disconnect.

In this case it is not a corporate laptop but the policy is also often imposed when you use a third party utility to control the WiFi connections. Many laptops come with these pre-installed.

Check your security settings, both in Windows itself and the WiFi driver if it is a third party add on. If there is a third party add on and it appears to be the problem, try deleting it. Just use Windows itself to control the WiFi.

Your gray cable is plugged into your ISP router and that is where your "Internet" is coming from. Some ISP routers like the Motorola surfboard only hand out 1 IP address. That one address is getting assigned to the first pc on your network since you are using the other router as a switch. When you plug in a second cable there is no internet access because your first PC already has the one address your ISP router is willing to give out. To resolve this

1. Plug your gray cable from your ISP router/modem into the internet port on your Dlink modem

2. The deault IP for your model Dlink is 192.168.0.1 Open an internet browser and put in that IP address. The default username is "admin" and default password is blank.

3. Setup your Dlink router. Link to some useful settings to use.

4. Plug your blue cable and up to three other Ethernet cables into the remaining Lan ports. As long as you setup DHCP on your Dlink you will be able to connect multiple PC's to your internet.