Ethertap is not available in 2.0 kernels so don't bother looking :-).

If you use tap you need to build a kernel with ethertap support.

If you build ethertap into the kernel it appears you only get
the one, tap0, interface. (This should probably be classes as
a bug if anyone wants to fix it)

If you build ethertap as a module you need to add lines like:

	alias tap0	ethertap
	options tap0	-o tap0 unit=0
	alias tap1	ethertap
	options tap1	-o tap1 unit=1
	...
	etc.

to your /etc/modules.conf.