With link aggregation, all of the controller ports need to connect to the same neighbor switch. If the neighbor switch goes down, the controller loses connectivity.
With many AP Managers, all of the controller ports !need to connect to the same neighbor switch. If the neighbor switch goes down, the controller !loses connectivity.
in case of multiple AP Managers, you can have LAPs connected to the WLC, directly/indirectly via multiple Switches.
in case of LAG, you must have the LAPs connected to the WLC, directly/indirectly via same Switch.
Incase of multiple AP Managers
You must assign a different AP-manager interface to each port on the controller.
The ports should be configured in sequential order such that AP-manager interface 2 is on port 2, AP-manager interface 3 is on port 3, and AP-manager interface 4 is on port 4.
all AP-manager interfaces must be on the same VLAN or IP subnet of the management interface. Preferably, all should be part of management interface's subnet
Logic of multiple AP Manager
From the discovery response that it receives, the access point can tell the number of AP-manager interfaces on the controller and the number of access points on each AP-manager interface. The access point generally joins the AP-manager with the least number of access points. In this way, the access point load is dynamically distributed across the multiple AP-manager interfaces.
Cons of multiple AP manager
if a port fails, then the lap reboots.
1.The 4402-50 controller supports a maximum of 50 access points and has two ports. To support the maximum number of access points, you would need to create two AP-manager interfaces. A problem arises, however, if you want to support port redundancy. the static AP-manager interface has port 1 assigned as the primary port and port 2 as the secondary, or backup, port. The second AP-manager interface has port 2 assigned as the primary and port 1 as the secondary. If either port fails, the controller would be left trying to support 50 access points on a port that supports only 48. As a result, two access points would be unable to communicate with the controller and would be forced to look for an alternate controller.
The 4404-100 controller supports up to 100 access points and has four ports. To support the maximum number of access points, you would need to create three (or more) AP-manager interfaces. If the primary port of one of the AP-manager interfaces fails, the controller clears the access points’ state, and the access points must reboot to reestablish communication with the controller using the normal controller join process. The Controller no longer includes the failed AP-manager interface in the LWAPP discovery responses. The access points then rejoin the controller and are load balanced among the available AP-manager interfaces.