In a global mesh deployment, using redundant controllers in the least restrictive regulatory domain ensures the highest number of channels available for backhaul. This design accommodates the varying regulatory constraints of different regions by adhering to the domain with the most lenient channel availability.

In a high-density environment where 5 GHz coverage is provided by nine APs, disabling the 2.4 GHz radios on some APs can reduce co-channel interference because the 2.4 GHz band has fewer non-overlapping channels. This approach helps maintain coverage while mitigating interference.

Mobility tunnels between Cisco Wireless LAN Controllers (WLCs) use UDP port 16666 for control messages and UDP port 16667 for data traffic. If EPING is failing, it indicates that the necessary ports are not open. Allowing UDP port 16666 through the firewall would enable the control messages required for establishing the mobility tunnels.

An RSSI value of -77 dBm is within the range that a 5 GHz radio can receive and decode, provided it's not below the RX-SOP threshold set for the RF profile. Since the RF profile is set to Medium for 802.11a, which operates in the 5 GHz band, the AP's 5 GHz radio will decode the frames.