Passed Exam Today 300-110

VLAN Select is a feature that allows for the dynamic assignment of clients to different VLANs from a pool based on various criteria, such as load balancing or location. In a centralized wireless deployment with N+1 high availability, if clients are receiving IP addresses from a different subnet after failover despite the WLANs being configured with the same dynamic interfaces, the issue is that the second controller ' s WLAN interface mapping resolves to a different VLAN or DHCP scope. VLAN Select ensures that client VLAN assignment is consistent regardless of which controller the client connects to, preventing the subnet change behavior observed during failover. Without VLAN Select, even identically named dynamic interfaces on two WLCs may map to different VLANs if the underlying switch configuration differs. RF Protocol (Option A) controls radio parameters. AP Groups (Option B) control SSID and VLAN assignments per AP cluster. AAA Override (Option D) allows RADIUS servers to assign per-user VLANs, which requires authentication — but these SSIDs use open authentication. Reference: WLSD Study Guide — N+1 High Availability Design, VLAN Select Feature, Consistent Client VLAN Assignment Across Controllers.

Devices that can tolerate at most 100 ms of delay when roaming are voice devices. The 100 ms maximum roaming delay threshold is the Cisco-specified design criterion for VoWLAN implementations — it defines the maximum time a handset can tolerate being disconnected from the wireless network during a roam event before the voice call is degraded or dropped. This threshold drives specific design requirements: 15-20% cell overlap at -67 dBm, fast roaming mechanisms (802.11r, CCKM, or OKC), and AP placement along user movement paths. Location services (Option A) have flexible latency requirements. Data applications (Option B) can tolerate much higher latency — typically several hundred milliseconds. Video (Option C) streaming has buffering mechanisms that allow for higher latency tolerance than real-time voice. Only voice applications have the strict 100 ms roaming delay requirement that directly influences the predictive design criteria. Reference: WLSD Study Guide — VoWLAN Roaming Design, Roaming Delay Requirements, Predictive Survey Criteria.

In a warehouse setting, two elements with a significant negative effect on wireless performance are AP height and absorption. AP height (Option B) is critical because warehouses often have very high ceilings (25-45 feet). When APs with internal (omnidirectional) antennas are mounted too high, the signal propagates primarily in the horizontal plane and the path loss to floor-level worker devices becomes excessive. Additionally, metal shelving between the AP and users further attenuates the already weak signal at high mounting heights. Absorption (Option E) is a major challenge in warehouses because the inventory stored on metal racks, particularly liquid goods, dry goods in cardboard, and dense materials, absorbs RF energy significantly. Metal racking causes both absorption and reflection, creating RF shadows and multipath environments that degrade connection quality. Wireless channels (Option A) are a design parameter, not an environmental impediment. Client authentication (Option C) and authorization (Option D) are network security processes unrelated to RF propagation quality. Reference: WLSD Study Guide — Warehouse Wireless Design, AP Height Considerations, RF Absorption in Industrial Environments.

For APs to be able to fail over between a primary SSO pair in one data center and a standalone WLC in a remote data center connected via WAN with firewalls, two design requirements must be met. First, a mobility tunnel must be created between the wireless controllers (Option A). The mobility tunnel enables the controllers to exchange mobility control messages, peer information, and eventually AP context when failover occurs. Without the mobility tunnel, the remote WLC is not recognized as a valid failover target by the APs through the mobility domain. Second, UDP ports 16666 and 16667 must be open through the firewalls between the controllers (Option D). UDP port 16666 is used for mobility control traffic and UDP port 16667 is used for mobility data traffic — both must be permitted through the firewalls at both data centers for the mobility tunnel to establish and function. HTTPS port 443 (Option B) is used for web management and API communication, not for mobility tunneling. A static RF group leader (Option C) is a RRM configuration unrelated to AP failover capability. Creating a mobility group with the same names (Option E) is a component of the configuration but alone is insufficient without the mobility tunnel and open firewall ports. Reference: WLSD Study Guide — Inter-Site WLC Failover Design, Mobility Tunnel Requirements, Firewall Port Planning for WAN-Separated Controllers.