BTW, i have the impression that the problem is related to routing in itself.
If i use, just like now, the DSL-Modem direct and bring up a ppp connection like this... ppp0 Protokoll:Punkt-zu-Punkt Verbindung inet Adresse:212.144.221.8 P-z-P:145.253.1.223 Maske:255.255.255.255 UP PUNKTZUPUNKT RUNNING NOARP MULTICAST MTU:1492 Metric:1 RX packets:66116 errors:0 dropped:0 overruns:0 frame:0 TX packets:119159 errors:0 dropped:0 overruns:0 carrier:0 Kollisionen:0 Sendewarteschlangenlänge:3 RX bytes:16271781 (15.5 MiB) TX bytes:97094173 (92.5 MiB) ... everything works fine. Because the different net ranges are routed and handled by the ppp0 interface, right? But when i use the router it's different and i would need to include the outside net's net range in my routing table, right? I tried this, but to no avail. But then, should not be the dlink be the one deciding what to do with packets for the outside net?