Dell MD3000i add secondary RAID controller

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I have an MD300i in operation running in simplex mode with one controller.  I want to add a second controller and change the configuration to duplex mode for redundancy and I am not sure how to correctly go about that.    I have found some documentation that says to slide the 2nd controller in partially and run an SMcli command to switch to duplex mode, followed by:

"Add the new management connection to MDSM with the following command:

SMcli 192.168.128.102 -c "set controller ethernetPort[1] ipAddress=10.37.121.54

gatewayIPAddress=10.37.112.1 subnetMask=255.255.240.0";

Where IP Address 192.168.128.102 is the current IP address of the new controller, and 10.37.121.54 is the

desired address"

What if I do not know the address on the new controller?  

I would appreciate any documentation or help that might lead me to my solution.  Thank you for your time.

Chris