network configuration problem

[Steve Bertrand]

> I've bought a router/gateway from my provider (Telekom/T-Online)
> which is called "Speedport W 502V Typ A" an has the ip address
> 192.168.2.1; it is connectet to an ethernet card (rl0).

192.168.2.1/24 is in a different network than 192.168.10.1/24. Your 
gateway and your workstation will not be able to communicate with one 
another.

> Then I assigned an address (e. g. 192.168.10.1) to the ethernet card
> with the help of

> and made it the default route:
> 
>     route add default 192.168.10.1

You essentially gave yourself an address outside of the gateways LAN 
address scope, and then proceeded to route all unknown traffic to yourself.

You probably want:

# ifconfig rl0 192.168.2.100 255.255.255.0

...and

# route add default 192.168.2.1

Then, for name resolution:

# echo "nameserver ip.of.isp.dns" >> /etc/resolv.conf

Regards,

Steve