300-110 Reviews Questions

In a Cisco Catalyst 9800 SSO deployment using Link Aggregation Group (LAG) for network interface redundancy, the SSO pair — WLC1 (active) and WLC2 (standby) — must both have their physical interfaces connected to the network infrastructure as part of the LAG bundle. LAG on the 9800 in an SSO configuration is implemented as a multi-chassis LAG across both the active and standby controllers. This means both WLC1 and WLC2 contribute physical member links to the port channel, and the connected switches must have LACP or PAgP bundle members from both controllers in the same port channel group. When an SSO failover occurs — WLC1 fails and WLC2 takes over as active — the LAG remains operational because WLC2 ' s physical links are already established members of the bundle and continue forwarding traffic without any link renegotiation. If only WLC1 had LAG connectivity and WLC2 had independent links, an SSO failover would cause a LAG topology change requiring re-convergence, introducing downtime. WLC3 is a separate N+1 backup controller joined via a mobility tunnel — not part of the SSO pair and its LAG configuration is independent. Reference: WLSD Study Guide — Catalyst 9800 SSO with LAG, Multi-Chassis Link Aggregation, High Availability Network Redundancy Design.

For a network supporting both data and voice over wireless, two key Cisco design recommendations apply. First, the 5 GHz radio band is recommended for voice over wireless due to its wider channel bandwidths, allowing for higher data rates and better quality of service for latency-sensitive applications. 40 MHz channels in the 5 GHz band provide significantly higher throughput than 20 MHz channels in 2.4 GHz, making Option B correct for the bandwidth reason stated. Second, setting the cell boundary to -67 dBm ensures sufficient signal strength for reliable voice communication at the cell edge, which is the Cisco standard threshold for VoWLAN coverage. Options C and E are partially correct (24 non-overlapping channels is accurate, 15-20% overlap is standard) but B and D are the primary Cisco recommendations that define the design targets for a predictive survey supporting voice. Reference: WLSD Study Guide — VoWLAN Design Requirements, Predictive Survey Design Criteria, 5 GHz Band Selection.

IEEE 802.11v BSS Transition Management is the standard that enables the network (via the AP) to actively provide roaming recommendations and suggestions to associated clients. When enabled on a SSID, the AP can send BSS Transition Management Request frames to clients, informing them of preferred target APs ranked by signal quality, load, and channel conditions. Critically, BSS Transition Management is a voluntary mechanism — clients that support 802.11v can act on the AP ' s recommendation, while clients that do not support 802.11v simply ignore the BSS Transition Request frames and continue operating normally. This selective applicability directly satisfies the requirement that non-VoWLAN clients must not be impacted. 802.11k (Option A) enables clients to build neighbor lists through measurement reports — this is a client-initiated process, not an AP-to-client recommendation. CCKM (Option B) is a Cisco proprietary fast roaming mechanism for legacy clients, unrelated to roaming guidance. 802.11r (Option D) accelerates the re-association handshake during roaming but does not provide proactive roaming recommendations. Reference: WLSD Study Guide — VoWLAN Design, 802.11v BSS Transition Management, Roaming Optimization Protocols.

The design requirements specify a multi-LAG configuration where each LAG connects to a single switch, different VLANs are assigned to different LAGs, the controller must dynamically learn partner LAG capabilities per port, and standby ports provide redundancy upon active port failure. These requirements collectively point to IEEE 802.3ad LACP (Link Aggregation Control Protocol) as the correct protocol. LACP is the industry-standard IEEE protocol that enables dynamic negotiation of LAG membership between endpoints — the WLC and each Catalyst 9300 switch exchange LACP PDUs (LACPDUs) to discover port capabilities, negotiate bundle membership, and monitor link status. LACP supports active and passive port states where active ports initiate negotiation and passive ports respond, and it provides the standby port mechanism through its hot-standby capability for link redundancy within the bundle. The requirement to ' learn the identity of partners that can support LAG capabilities ' is the defining characteristic of LACP ' s standardized PDU exchange mechanism. PAgP (Option C) is a Cisco proprietary port aggregation protocol that, while functionally similar, is not the IEEE standard and is incompatible with non-Cisco equipment in mixed environments. OSPF (Option B) and BGP (Option D) are Layer 3 routing protocols entirely unrelated to port channel negotiation. Reference: WLSD Study Guide — Catalyst 9800 LAG Configuration, LACP IEEE 802.3ad, Multi-LAG High Availability Design.