I have successfully installed Oracle R12 instance in Oracle Virtual Box in my home PC. However I can not connect to the R12 instance from outside PC. I have bitdefender 2012 installed in my home Vista machine. What firewall changes do I need to make? I am sure its a firewall issue. I can access the instance from inside Linux box and from host PC. Thanks...My home PC is Vista with Oracle Virtual Box (Linux) and my work PC is windows 7 Professional

1- What is your linux network type "Bridge", Host-only, or NAT?
2- Confirm if you have disabled linux firewall as explained in videos
3- Issue ifconfig command on linux and let me know the IP address.
4- Confirm if you have placed the same IP address on your Windows hosts file.

linux network type: Host Only
Linux firewall is disabled
ifconfig ip: inet addr:192.168.56.101 Bcast:255.255.255.255 Mask:192.0.0.0
Windows host file has the same IP address...FYI, I can access R12 from inside linux and from host computer but not from other PCs.
My netmask: 192.0.0.0
My gateway: 255.255.255.0...attached is the result

1) Why is your linux network type set to Host-Only? Is that because you dont have a router? Please confirm.
2) Your above settings does not look right. For example your gateway IP seems to be incorrect.

Could you please upload the screen shot of ifconfig command from Linux.

Also please upload the screen shot of your network configuration as shown in this video:
http://handsonerp.com/oracle-financials-tutorials/76-03-oracle-e-business-suite-installation-inst/6334-configuring-virtual-machine-network.html