why does my iMac has two IP addresses registered?
Solution 1:
I have 4 IP addresses on some of my Mac's network interfaces since I set them up in network preferences control panel.
You could go there and delete all un-needed IP addresses or at least know it's not something that was intended.
Solution 2:
Depending on you LAN setup, this can happen if the computer has ethernet and wifi both turned on.
You can verify from the Mac in System Preferences->Network: if both Ethernet and Wifi are green that's it.
In this case the Mac will use the first one listed--- either make sure the faster connection is first or turn off the slower.