Cisco 300-425 - Designing Cisco Enterprise Wireless Networks (ENWLSD)

In a medical treatment environment where both data and voice services are required, continuous coverage of -67 dBm from one access point is the minimum requirement. This ensures that there is sufficient signal strength for reliable voice communication, which is critical in medical settings. The -67 dBm threshold is commonly recommended for voice applications to ensure call quality and reliability.

So -67dBm covers both Data & Voice with a single AP

Aggregated Probe Response Optimization should be enabled on the controller to optimize roaming, especially for environments with a high density of Apple OS devices. This feature reduces airtime consumption and overhead by aggregating probe responses, which can improve the roaming experience for the employees.

 Cisco 3800 Series APs support higher speeds provided by IEEE 802.11ac Wave 2, which Fast Ethernet switches cannot fully support. Replacing them with mGig or gigabit switches with 10G uplinks will ensure the infrastructure can handle the increased data rates. The CAT 6A standard supports these speeds, so there’s no need to replace the wiring if it’s already CAT 6A.

 For a WLAN design that supports services like internet, email, voice, and database access, a signal strength of -67 dBm is considered good for voice and streaming services. A 25-dB SNR (Signal-to-Noise Ratio) is also desirable for high-quality voice and video applications, and a maximum of 1 percent packet loss is acceptable to ensure reliable connectivity and service quality.

https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/116057site-survey-guidelines-wlan-00.html

 Frequent disconnections may occur if the RSSI threshold set for optimized roaming is too high, causing clients to attempt roaming too late. Disabling optimized roaming and enabling 802.11v support allows for better client steering by the AP, as 802.11v includes the BSS Transition Management feature, which guides clients to a better AP based on the network’s conditions.

Creating a mobility group requires that all Wireless LAN Controllers (WLCs) share the same mobility group name. This allows them to recognize each other as peers and participate in client mobility events. The WLCs must be defined as peers in each other’s static mobility members list to facilitate inter-controller communication and roaming.

In Cisco wireless networks, access points can be configured with failover priorities ranging from 1 to 4, with 1 being the highest priority and 4 being the lowest. An access point with priority 1 is considered critical and will be given preferential treatment in failover situations, ensuring that it reconnects to a backup controller before access points with lower priorities

 The issue described is indicative of a hidden node problem, where MAP-1 and MAP-3 cannot hear each other’s transmissions but can both communicate with RAP-2. This leads to frame collisions as both MAPs may attempt to transmit at the same time, unaware of the other’s actions. The design needs to address this by implementing mechanisms such as RTS/CTS or adjusting the placement of the APs to avoid this issue.

https://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob30dg/WiMesh.pdf

 For mobility between two buildings with one controller at each site, CAPWAP data and control traffic must be able to pass between controllers. CAPWAP control messages use UDP port 5246 while CAPWAP data messages use UDP port 5247; therefore, these ports must be open to allow inter-controller communication for seamless mobility. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)