When I extend my WiFi-Network with a AirPort TC there is a conflict 192.168. vs. 169.154.

No, I'm sorry for the confusion. The AirPort Time Capsule needs to be configured to operate in Bridge Mode.

If you use the AirPort Utility setup "wizard", it will automatically configure the Time Capsule for you correctly. Here is what I would suggest:

Perform a Hard Reset on the AirPort Time Capsule again so that the network settings will be reset back to default settings.

Temporarily.......Move the Time Capsule close to the AirPort Express.....(or is it an AirPort Extreme?) and connect a short spare Ethernet cable from a LAN <--> port on the AirPort Extreme to the WAN "O" port on the AirPort Time Capsule.

Click on the WiFi menu at the top of the screen and look for a listing of New AirPort Base Station

Just below that listing, click directly on AirPort Time Capsule

When you click on AirPort Time Capsule, that will start up the AirPort Utility setup "wizard". The wizard will take a few seconds to analyze the network and then display a screen that looks like the example below except that you will see your devices pictured.

In the example below, you can see that an AirPort Express is being set up to extend an AirPort Extreme. Your screen will show that the AirPort Time Capsule will be set up to extend the AirPort Express (or AirPort Extreme).

Base Station Name........Type in a device name for the AirPort Time Capsule

Click Next

Now watch the next screen very carefully to see that the AirPort Time Capsule is being set up to "extend using Ethernet". This will confirm that the setup wizard has picked up the wired Ethernet cable connection so it will apply the correct settings to the AirPort Time Capsule.

When you see the message of Setup Complete, click Done.

Now power off the AirPort Time Capsule and move it back to the remote location on your network and connect the network Ethernet cable to the WAN "O" port.

Power up the AirPort Time Capsule and you should be all set.

As a test, hook the AirPort Time Capsule back up directly to the AirPort Extreme. Power off and restart every device on your network.

Do things work that way?

If yes, then you probably have a problem with your Ethernet wiring or Ethernet hubs/switches since you know that the Time Capsule is set up correctly.

I tryed to configure it without WiFI, direct via Ethernet plugged with a Laptop but every time I turn it on int the WiFi-Network this crashs because of the 192.168.# vs. 169.154.# conflict.

Sorry, I am not clear on whether the AirPort Time Capsule normally connects to the AirPort Express network using a wired Ethernet cable connection, or whether the AirPort Time Capsule normally connects to the AirPort Express WiFi network using only a wireless connection.

Can you clarify on that?

Now, if I connect my AirPort TC this becomes a 192.168.# Address but gives all mobile devices 169.154.# Addresses that make the WiFi-Network not working.

The AirPort Time Capsule should be set up in Bridge Mode to work with the AirPort Express, and in Bridge Mode, the AirPort Time Capsule does not assign IP addresses at all. Your "main" router.....the AirPort Express.....provides the IP addresses and the AirPort Time Capsule passes them through to other devices.

A "169.154.x.x" IP is known as a self-assigned IP address. Devices are assigning this IP address to themselves because they are not receiving a valid IP address from your network.

A few questions if you don't mind:

• What is the make & model of the Internet router that you connect the AirPort Express to directly by Ethernet?
• Does this router perform as your "main" router?
• Does this router also provide a wireless network?
• Is the TC configured to extend the Express? If so, does the TC connect back to the Express by wireless or by wire?

Nice work! I am looking forward to visiting Italy later this month.