uml vde transport
Finally, starting from Linux 2.6.24-rc1,
you can use native vde transport for user-mode linux.
uml-vde-transport's syntax is:
ethN=vde,<vde_switch>,<mac addr>,<port>,<group>,<mode>,<description>
E.g. you can use it in this way:
$ linux ubd0=uml-image mem=128k eth0=vde,/tmp/switch1