This doesn't work on Kubuntu 6.10 with RealTek (module r8169) cards.

mode=0 works sometimes - and this may be problematic because I have two dumb switches cascaded, however any other applicable mode (mode=6 for example) will not even initialize the interface.  Any attempts to manipulate the interface after that causes a partial system lock up. 

mii-tool doesn't work with those cards either, however, ethtool presents the same output as described.

Any feed back on this would be appreciated, and I'll be testing mode=0 on a single switch in the next week.