Basic questions about MIMO on USRP2

Hi all,

I have several basic questions on about build a MIMO system with two
USRP2s. I have my master board connect with the computer and the
external clock. The slave board is connected to the master by the MIMO
cable. I am working C++ and I have the SISO working now. My questions
are as follows:

1 Do I need to rebuild the firmware and FPGA code for the master USRP2?

2 How I can identify which one is the master board which one is the
slave in the code?
3 Do I need to call the make(interface, mac_addr_str) function twice ?
4 How can I get the mac_addr_str values for the slave and the master
board ?

Best Regards!