If you want to make a TeamViewer connection, you can either make a classic TeamViewer connection using the TeamViewer ID and the TeamViewer password of the remote computer or you can make a connection to another computer in your LAN using the IP address and a password.
How to establish a regular TeamViewer connection?
The regular TeamViewer connection is simple to establish and the connections are working accross platforms and behind firewalls and proxys. Here is a little guidance of how to establish a connection:
1. Enter your partner‘s TeamViewer ID in the “Remote control” tab under Partner-ID. Click on Connect to partner, and enter your partner‘s password in the following dialog box in order to establish a connection. That´s it :-)

How to establish a TeamViewer LAN connection?
If you would like to establish a connection in your LAN, you need to set up theTeamViewer on the remote computer a little bit.
1. Go into the TeamViewer Options --> General --> Incoming LAN Connections --> Accept or Accept exclusively

Note: If you choose Accept exclusively no regular TeamViewer connection is possible and the Computer & Contacts list can´t be reached since the TeamViewer does not longer have a connection to the internet.
2. When you chosse Accept exclusively you will see the internal IP address on the main window of your TeamViewer application

Note: If you choose Accept, regular TeamViewer connections are still possible. You just need to find out the remote computers internal IP address. You can easily do this by opening the Command Promt and type in:
ipconfig
3. To start the TeamViewer LAN connection, please make sure, that you are in the same network.
4. On your computer: Enter your partner‘s IP address in the “Remote control” tab under Partner-ID. Click on Connect to partner, and enter your partner‘s password in the following dialog box in order to establish a connection. That´s it :-)
Now you are having a LAN connection to the remote computer without a connection to the internet.
Note: In LAN Connections are the Connection reportings disabled.