Switch off WPS (disable) and configure Wireless Security without key (free wireless access). After that configuration you have to wireless access to router for 100%.

jimasek wrote

Switch off WPS (disable) and configure Wireless Security without key (free wireless access).

I did both, but after choosing Dynamic IP, the router doesn't answer under 192.168.0.254.

DHCP is enable on router? After configuration WAN only your access to router is only by the wireless. At this monent LAN socket is WAN port.

According to the web interface of the router, the dhcp server of the device will not start, if the dynamic IP mode is chosen.

I mean DHCP on Wireless to get you address on wireless card.

There is only one dhcp server to configure. The warning is shown in the following picture:

https://dl.dropbox.com/u/20555698/status1.png.

When you change it the WAN only, the ethernet port on the router will be WAN port, and you can only access internet or the interface page 192.168.0.254 by the wireless connection.
the ethernet port of the router is connected to the cable modem.
You can try to reset it and reconfigure it. Switch the router to 3G mode and connect to the wireless network on your computer.
login to 192.168.0.254 and Quick Setup-> Choose WAN only -> Dynamic IP.

Thank you joyce, now everything works fine.
The crucial note was to switch the router to 3G mode, which is a bit confusing, since 3G is a mobile communication standard and I have a cable modem. But nevertheless it works. Important is also to clone the MAC address of the ethernet controller of the computer and not of the wireless controller (which is suggested in the interface because the connection from the computer to the router is wireless).

I observed some interesting/strange behavior.
To use an UMTS stick I changed the internet access mode from WAN only to 3G/4G only and everything worked well.
Back at home a forgot to change it again and plugged my cable modem in the ethernet port of the router and it also worked.
Although 3G/4G only mode is activated, the ethernet port is used as WAN. Is it supposed to work that way?

In 3G/4G only mode, ethernet port is acting as a LAN port. If your modem is plugged it, actually, it is working like a wireless access point,
You should not be able to share internet with TP router.