If I have an older WLC 6000 series one network and a 7210 on another.
Then I have some existing AP's on the 6000 and I'm adding new 225's on the same network however I want them to join the 7210 controller. I'm guessing I only have 3 ways:
1) I console into each AP and specify the controller
2) I let them join the old controller and then put them on the new one since the DHCP scope points to the old controller
3) I create a new DHCP scope for the acces points and pointing DHCP option 43 to the new WLC.