Im not sure what you're saying when you say "identical". NIC cards all have different addresses. There are two identifiers on a NIC card that together comprise the MAC address. One is vendor specific and that number (different for each vendor) as well as the second number (serial number) is "burned" into the card. You can get a card that will emulate another number (IE in routers) but that is used for something else. So if I understand your question correctly, you will not be able to do what you are asking. The NIC cards are set up this way to prevent confusion on networks.
Okay, I assuming that you mean you bought two of these cards "off the shelf". In this case, you can use both of these on the same network because they will have different MAC address. The addresses should show differently in HEX format. The last portion of the address being the serial number(s).
Yes. No two NIC cards are the same, even though they may be the same model and brand. NIC cards have a physical MAC address built into them. This address can not be changed (unless you are using a software NIC. These NICs can be changed, but are only available on a few amount of mobos).
MAC addresses are 48 bit hex codes. The first 24 bits are the manufactor code. For example, SiS NICs start with 00-D0-09, my Intel Pro nic starts with 00-08-C7. The last 24 bits are the serial number of the nic.
You'll get the double speed compared to one card. I'm not sure if this is true for a hub since the traffic is shared on all ports, but it would be true for a switch. This method is used on servers that require very high bandwidth. Your computer will also have two IP:s. Besides the speed you get is normally capped b other factors than the card itself (hdd, pci-bus and so on) so in a workstation there's really no point in having two cards on the same hub.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS