[CentOS-virt] dummy ethernet interfaces

I have a 32bit(PAE) CentOS5 machine running (stock CentOS) Xen. I've been using the kernel dummy ethernet driver to create interfaces on the host machine so that I can create internal networks for the guests and host to communicate with each other. The only issue I have with this is that the interface is not >=100MB, but is 10MB.

Is there a way I can increase the speed of these interfaces (I've tried looking at the kernel docs and google'ing) or another dummy style interface driver I can use to create these?

Thanks!

--Caitlyn