There are (completely different) bridging options in 2.0, 2.2, and 2.4. It *seems* to work (I'm trying to work with user-mode-linux, and bridging from the tap interface to the real one is the "easy" way to get a u-m-l pseudo-machine on the net, and it doesn't work but I think the helper app is the problem, the bridging support seems fine...) One uses brcfg, one uses brctl.