I am using two virutal machines each in different PC’s (PC-1 Windows (vm-ubuntu12.04), PC-2 Windows server 2008 (vm-ubuntu 12.04). I have connected 2 windows PC’s to the switch and each VM to their respective hosts using bridge adapter and all the 4 four are able to ping each other. There is no routing. i.e all the 4 are in the same subnet. I have configured asterisk server and one sip in one of the ubuntu machines, and other sip in other PC. both are registered sip’s. I am able to make the calls hear the ring sound but when picked could not hear the voice. If further information needed please let me know.