An article I wrote a few months ago explained how to use Quagga on a Linux host to emulate BGP-speaking router inserting test routes into your lab network. If you need multiple BGP sources, you can use a few simple tricks to run numerous BGP daemons on the same host.
Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.