Given that it's 2 years old, I assume your questions are answered. "What is the purpose of the wireless management interface on Cisco 9800's", just in case. Wireless LAN Controllers, Cisco 9800's included, manage APs. This is the interface used for CAPWAP communication with your APs and requires a certificate "TrustPoint" to be attached to the interface for APs to join and communicate with the controller. If you are using Cisco 9800_CL controllers there is no factory MIC installed, you have to use the setup script to define time, country code, and wireless management interface settings, and it will generate the cert = trustpoint, attach to the interface you specify. This is the interface you want your APs pointed to. On the 9800_CL, it's a VLAN/SVI which is created for this purpose. Really on any of the 9800's you want to use EtherChannel for all data communication including your AP Mgmt interface, so would be VLAN/SVI on your Etherchannel group. 9800_CL that's Gig2 by default should be an 802.1Q trunk w promiscuous mode enabled on your vSwitch in VMWARE. There's also an OOB - Out of Band Management interface, Gig1 used to manage the controller itself, and used as the default source interface for AAA services, and telemetry. on the 9800_CL Gig3 is for HA purposes. Technically you could add several other interfaces up to 11, but this is the default on the 9800_CL. If you go back far enough AireOS used to require a separate management interface, to AP Manager interface, and then they started just using 1 interface for both management of the controller, and AP management, but it is important to understand AP managers are used for CAPWAP coms to the APs. Hope this helps someone searching for this issue. A student in my C9800 class at WiFi Training told me he noticed this question, so figured I would help the next visitor.
