Link aggregation (LAG) is a partial implementation of the 802.3ad port aggregation standard. It bundles all of the controller's distribution system ports into a single 802.3ad port channel.
Restriction for Link aggregation:
- LAG requires the EtherChannel to be configured for 'mode on' on both the controller and the Catalyst switch -> Answer B is not correct.
- If the recommended load-balancing method cannot be configured on the Catalyst switch, then configure the LAG connection as a single member link or disable LAG on the controller -> Answer A is not correct while answer D is correct.
Reference: https://www.cisco.com/c/en/us/td/docs/wireless/controller/7-5/configuration-guide/b_cg75/b_cg75_chapter_0100010.html