Configuring a high availability SSO pair on Cisco Catalyst 9800 IOS XE WLCs has specific technical prerequisites that must be satisfied for the SSO relationship to form and function correctly. The two critical requirements are: each WLC must have a unique Redundancy Management Interface (RMI) IP address (Option B), and both WLCs must run identical IOS XE software versions (Option D). The Redundancy Management Interface is the dedicated in-band control channel over which the active and standby WLCs exchange state synchronization information, keepalive messages, and configuration updates. Each controller requires its own unique RMI IP address within the same subnet - the active uses one address and the standby uses another. If they shared the same RMI IP (Option C), there would be an IP address conflict preventing the interface from functioning. Identical software versions (Option D) are mandatory because the SSO state synchronization protocol and data structures must be version-compatible between the active and standby controllers. Any mismatch in IOS XE version will prevent SSO formation. License count (Option A) does not need to be identical for SSO. Service port IP addresses (Option E) must be unique per controller, not identical.
Reference: WLSD Study Guide - Catalyst 9800 SSO Prerequisites, Redundancy Management Interface Configuration, High Availability Pair Formation Requirements.

The requirement for users to retain their session state and IP address when roaming between buildings managed by different WLCs is a Layer 3 roaming scenario. In Cisco ' s wireless architecture, IP address preservation across controller boundaries is achieved through inter-controller mobility - specifically the foreign-anchor mobility tunnel mechanism. When a client roams from Building A (WLC-A) to Building B (WLC-B), WLC-B becomes the foreign controller and WLC-A becomes the anchor controller. WLC-B tunnels the client ' s traffic back to WLC-A, allowing the client to retain its original IP address even while physically associated to an AP managed by WLC-B. This requires a mobility tunnel between WLC-A and WLC-B with both controllers configured in the same mobility group name - the group name is the trust identifier that permits the mobility tunnel and anchor-foreign relationship to form. Without the same group name, the controllers will not form a trusted mobility peer relationship. AP groups (Option C) control SSID and VLAN assignments per AP cluster but have no impact on inter-controller roaming. HA cluster configuration (Option B) creates SSO redundancy, not roaming capability between separate N+1 controllers.
Redundancy port connection (Option D) is used for SSO keepalive and state sync, not mobility tunneling.
Reference: WLSD Study Guide - Inter-Controller Mobility, Mobility Tunnels, Layer 3 Roaming and IP Address Preservation.

Cisco WLC AP Failover Priority governs the order in which APs are processed when a WLC recovers and APs begin re-associating. The priority levels are: Critical, High, Medium, and Low. During recovery situations, the WLC will accept and process AP join requests in order of priority - Critical priority APs are processed first, before all other priority levels. In a deployment where the WLC is located in a remote data center connected via WAN, the join process for all APs is slower due to WAN latency and potential bandwidth constraints. Under these conditions, assigning Critical priority to executive office APs ensures they are at the front of the processing queue and restore service before lower-priority APs. The executive office designation implies business-critical operations requiring the fastest possible wireless restoration - a requirement that directly maps to the Critical priority level. High priority (Option A) would position the executive APs second in the queue behind any Critical priority APs. Medium (Option B) and Low (Option C) would place them further down the processing order. Reference: WLSD Study Guide - AP Failover Priority Configuration, N+1 and SSO Redundancy Design, WAN-Linked Controller Deployments.

Cisco Spectrum Expert is a dedicated spectrum analysis tool designed to identify and analyze non-Wi-Fi interference sources at Layer 1. During a post-deployment site survey, it can detect interference from various devices such as cordless phones, Bluetooth devices, microwave ovens, video cameras, and other unlicensed RF emitters. The tool provides a visual representation of the RF environment across the frequency spectrum, allowing engineers to pinpoint the exact source of interference and characterize it by duty cycle, frequency, and interference pattern. A network analysis module (Option A) operates at Layer 2 and above, unable to detect non-802.11 RF emissions. Wireless intrusion prevention (Option B) detects rogue APs and 802.11 attacks but not Layer 1 RF noise. Wireshark (Option C) is a packet capture tool for Layer 2-7 analysis and cannot detect non-Wi-Fi RF energy. Reference: WLSD Study Guide - Layer 1 Spectrum Analysis, Post- Deployment Survey, Non-Wi-Fi Interference Identification.

Cisco Spectrum Expert is a dedicated spectrum analysis tool designed to identify and analyze non-Wi-Fi interference sources at Layer 1. During a post-deployment site survey, it can detect interference from various devices such as cordless phones, Bluetooth devices, microwave ovens, video cameras, and other unlicensed RF emitters. The tool provides a visual representation of the RF environment across the frequency spectrum, allowing engineers to pinpoint the exact source of interference and characterize it by duty cycle, frequency, and interference pattern. A network analysis module (Option A) operates at Layer 2 and above, unable to detect non-802.11 RF emissions. Wireless intrusion prevention (Option B) detects rogue APs and 802.11 attacks but not Layer 1 RF noise. Wireshark (Option C) is a packet capture tool for Layer 2-7 analysis and cannot detect non-Wi-Fi RF energy. Reference: WLSD Study Guide - Layer 1 Spectrum Analysis, Post- Deployment Survey, Non-Wi-Fi Interference Identification.