multiple virtual network ports using a single physical port

I am a little unclear how, or if it is possible, to create multiple virtual network ports which use the same physical port on a server. I am creating a test Oracle RAC cluster and it needs to have 2 ethernet ports but there is only one ethernet card in the server. Is this possible and is there any documentation that outline how?

Thanks,
Steve

hi tom, do you know if there is some limitation based on hardware? i think not all nic supports IEEE802.11Q.
Any way to check if the VLAN trunking is supported? cat /proc/pci or similar?

thanks!