I think your doing RAC practice in virtual box.
As you used the Internal Network, You should configure both the Ethernet cards as host only.
Thanks for your reply,
I am using VMWARE WORKSTATION 9 WITH RHEL 5
You can use the both Networks Cards on Bridge. I have 3 Racs on production environments with this configuration but is OVM.
Here is a installation tutorial, step by step (2 Network cards with bridge) on VMWare
I hope this help you