How to set speed of eth0?

I am running SuSE8.1 pro, and I want to reduce the speed of my ethernet card to 10M half duplex. (Currently 100MB full duplex) How do I do this? I have tried YAST2, it allows me to set the IP address etc, but there is nothing about the speed? It could do it in WindowsXP, but how do I do it under SuE Linux? I was asked by my ADSL modem/router supplier to do this and a few other things in order to prevent problems with my router, which hangs sometimes. -- Frits Wüthrich