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Question 181. What is a primary function of the Catalyst 9800 redundancy port

1. Assign client VLANs
2. Provide DNS resolution
3. Synchronize HA state
4. Authenticate wireless clients

Correct Answer: 3. Synchronize HA state

Explanation:

The redundancy port provides communication between the active and standby Catalyst 9800 controllers in an HA SSO pair. It transports synchronization information, control messages, keepalive traffic, role information, and operational state between the controllers. Configuration and important runtime information are replicated so the standby controller can assume the active role after a failure. The redundancy connection is therefore a critical component of stateful high availability. It is not used for ordinary wireless client authentication or VLAN assignment. Proper redundancy connectivity must be maintained to preserve synchronization between the two controllers.

Question 182. What is a major purpose of the Redundancy Management Interface

1. Check gateway reachability
2. Assign RF channels
3. Configure guest WLANs
4. Provide DHCP addresses

Correct Answer: 1. Check gateway reachability

Explanation:

The Redundancy Management Interface provides an additional high availability communication path between the active and standby Catalyst 9800 controllers. One of its important functions is gateway reachability monitoring. This helps the HA pair distinguish certain network failures from a complete controller failure and make better switchover decisions. The RMI uses addresses associated with the management network and complements the main redundancy port. Cisco introduced RMI to improve HA resiliency and reduce situations where a simple redundancy link problem could result in incorrect failover behavior.

Question 183. What is the maximum supported round trip latency for a Catalyst 9800 redundancy port link

1. 20 milliseconds
2. 40 milliseconds
3. 60 milliseconds
4. 80 milliseconds

Correct Answer: 4. 80 milliseconds

Explanation:

Cisco specifies a maximum round trip latency of 80 milliseconds for the redundancy port link between Catalyst 9800 controllers in an HA deployment. High availability synchronization requires timely communication between the active and standby units, so excessive latency can affect state replication and failover behavior. Designers placing controllers in different locations must validate the complete network path rather than assuming any routed connection is suitable. Latency, bandwidth, and MTU are all important HA design requirements. A link exceeding the supported latency should not be used for the controller redundancy connection.

Question 184. What minimum bandwidth does Cisco specify for the HA redundancy port link

1. 10 Mbps
2. 60 Mbps
3. 100 Mbps
4. 1 Gbps

Correct Answer: 2. 60 Mbps

Explanation:

Cisco specifies a minimum bandwidth of 60 Mbps for the redundancy port link used by Catalyst 9800 high availability controllers. This bandwidth supports configuration synchronization, operational state replication, keepalive communication, and other HA traffic exchanged between the active and standby units. The redundancy link should therefore be designed as a reliable infrastructure connection rather than treated as a low bandwidth management path. Designers must evaluate latency and MTU requirements at the same time because all three parameters affect whether the HA link meets Cisco deployment requirements.

Question 185. What minimum MTU is required on the Catalyst 9800 redundancy port link

1. 1500 bytes
2. 576 bytes
3. 1000 bytes
4. 900 bytes

Correct Answer: 1. 1500 bytes

Explanation:

Cisco requires the Catalyst 9800 redundancy port path to support a minimum MTU of 1500 bytes. The redundancy connection carries synchronization and control information between the active and standby controllers, and the complete path must accommodate the required packet size. An intermediate network that reduces the supported MTU can interfere with proper HA communication. Designers deploying controller pairs across network infrastructure should verify MTU end to end along with the required bandwidth and round trip latency. These checks are particularly important when controllers are located on separate virtualization hosts or across different physical locations.

Question 186. What software requirement applies to controllers forming an HA SSO pair

1. Different releases are preferred
2. Only the standby needs software
3. Both should run the same software version
4. Software versions do not matter

Correct Answer: 3. Both should run the same software version

Explanation:

Controllers forming a Catalyst 9800 HA SSO pair should run the same Cisco IOS XE software version. Matching software ensures that both systems have compatible configuration structures, runtime processes, and state synchronization behavior. Cisco also provides software mechanisms in newer releases that can assist with upgrading the standby controller when versions differ, but the completed HA pair must operate with compatible software. Designers should verify software versions before establishing redundancy, especially when replacing hardware or rebuilding a failed standby controller. Consistent software helps reduce unexpected synchronization and switchover problems.

Question 187. Which hardware requirement applies to physical controllers in an HA pair

1. Different controller families
2. Matching product identifiers
3. Different port counts
4. Different power supplies

Correct Answer: 2. Matching product identifiers

Explanation:

Cisco HA design guidance requires the two Catalyst 9800 controllers in an HA pair to use the same supported product identifier. Matching platforms provide equivalent hardware capability and ensure that the standby controller can assume the active role without creating a capacity or platform mismatch. Virtual Catalyst 9800 deployments have similar requirements for matching host environments and allocated computing resources. HA should therefore be planned as a matched pair rather than combining unrelated controller platforms. Hardware compatibility should be verified before the redundancy configuration is attempted.

Question 188. What happens to the wireless management address after two Catalyst 9800 controllers form an HA SSO pair

1. Each AP receives a new address
2. Both addresses are removed
3. The standby uses DHCP only
4. The pair presents one shared management address

Correct Answer: 4. The pair presents one shared management address

Explanation:

After an HA SSO pair is formed, external systems interact with the controller pair through a shared wireless management address. The active controller currently owns the operational role, while the standby maintains synchronized state and can assume control after a switchover. Access points, clients, management platforms, and other network services therefore continue using the same controller address rather than learning a completely different management address after every failover. This design helps make an SSO transition transparent to much of the surrounding network infrastructure.

Question 189. What is synchronized from the active controller to the HA standby

1. AP and client state
2. Building floor material
3. Client antenna type
4. Internet routing tables only

Correct Answer: 3. AP and client state

Explanation:

In HA SSO, the active controller synchronizes important access point and wireless client state with the hot standby controller. This state replication allows the standby unit to take over without forcing supported APs and established clients to completely rebuild their wireless sessions. Cisco specifically describes synchronization of access points in appropriate operational states and clients in the RUN state. Some transitional client or AP states may not receive the same seamless treatment. The overall goal is to minimize service disruption during an active controller failure.

Question 190. How many CAPWAP tunnels does an AP maintain to an HA SSO controller pair at one time

1. One
2. Two
3. Three
4. Four

Correct Answer: 1. One

Explanation:

An access point maintains one active CAPWAP tunnel to the controller that currently holds the active role in a Catalyst 9800 HA SSO pair. The AP does not maintain a second independent active tunnel to the standby controller. Instead, the active controller synchronizes AP state with the hot standby. If a switchover occurs, the synchronized standby becomes active and continues serving the AP. This architecture provides stateful resiliency without requiring every access point to maintain duplicate active CAPWAP sessions to both controller units simultaneously.

Question 191. What normally happens to joined APs during a successful HA SSO switchover

1. They factory reset
2. They enter mesh mode
3. They download new software
4. They avoid returning to Discovery state

Correct Answer: 4. They avoid returning to Discovery state

Explanation:

A key benefit of Catalyst 9800 HA SSO is that supported joined access points do not return to the Discovery state when the active controller fails and the synchronized standby takes over. Their CAPWAP state has already been replicated to the standby unit. This reduces the amount of time needed to restore wireless service compared with stateless redundancy, where APs may need to rediscover and rejoin another controller. Stateful failover is therefore particularly important in environments where wireless availability and application continuity are major requirements.

Question 192. What is a primary benefit of controller link aggregation

1. Client authentication
2. Redundancy and additional bandwidth
3. Radar avoidance
4. AP certificate creation

Correct Answer: 2. Redundancy and additional bandwidth

Explanation:

Link aggregation combines multiple physical controller interfaces into one logical port channel. Cisco recommends LAG when several physical uplinks to the same switching infrastructure are available because it can provide both increased aggregate bandwidth and link redundancy. If one member link fails, traffic can continue through remaining operational members. The logical port channel also simplifies connectivity compared with treating every physical link as an independent controller interface. Proper switch configuration and consistent Layer 2 settings are essential for reliable LAG operation.

Question 193. What happens when one physical member of a Catalyst 9800 LAG fails

1. Traffic uses remaining functioning links
2. Every AP disconnects immediately
3. The controller deletes the WLAN
4. All radios shut down

Correct Answer: 1. Traffic uses remaining functioning links

Explanation:

A major advantage of link aggregation is that traffic can move to the remaining functioning member links when one physical controller uplink fails. As long as at least one suitable member remains operational, the controller can continue carrying network traffic through the logical port channel. This improves wired infrastructure resilience and reduces the chance that a single cable or switch port failure will isolate the wireless controller. Designers should still provide appropriate switching redundancy because a port channel connected entirely to one failed upstream device may not protect against every infrastructure failure.

Question 194. How should Layer 2 settings be configured across ports in one controller LAG

1. Every port should use different VLANs
2. Only one port carries VLANs
3. The settings should be unrelated
4. The settings should match

Correct Answer: 4. The settings should match

Explanation:

Cisco recommends consistent Layer 2 configuration across all physical interfaces participating in the same Catalyst 9800 port channel. For example, designers should not permit a VLAN on one member while filtering that same VLAN from another member. Inconsistent configuration can cause traffic forwarding problems because the controller treats the member links as one logical interface. The neighboring switch configuration must also correspond correctly with the controller port channel. Consistency is therefore essential for predictable load distribution, redundancy, and VLAN forwarding across the aggregated connection.

Question 195. Which DHCP option provides an IPv4 controller address to an AP

1. Option 6
2. Option 43
3. Option 52
4. Option 82

Correct Answer: 2. Option 43

Explanation:

DHCP Option 43 can provide a Cisco access point with the IPv4 address of a wireless controller during the discovery process. This is especially useful when the AP and controller are located on different IP networks because simple local broadcast discovery cannot cross routed boundaries. The AP can receive its normal IPv4 configuration and controller discovery information through DHCP, then send CAPWAP discovery or join messages toward the learned controller. Cisco identifies Option 43 as a common discovery method for large distributed wireless deployments.

Question 196. Which DHCP option can provide an IPv6 wireless controller address

1. Option 82
2. Option 43
3. Option 6
4. Option 52

Correct Answer: 4. Option 52

Explanation:

DHCP Option 52 can provide Cisco access points with IPv6 addresses of wireless controllers during the AP discovery process. It serves a similar purpose for IPv6 environments to the role that Option 43 commonly performs for IPv4 discovery. This is useful when access points and controllers are separated by routed infrastructure and local broadcast discovery is not sufficient. Cisco documents both IPv4 and IPv6 controller discovery methods so wireless infrastructure can be designed for different addressing models and deployment requirements.

Question 197. Which DNS name can Cisco APs query to discover a controller

1. cisco capwap controller localdomain
2. wireless dhcp server localdomain
3. cisco radius controller localdomain
4. catalyst rf manager localdomain

Correct Answer: 1. cisco capwap controller localdomain

Explanation:

Cisco access points can use DNS discovery by querying the Cisco CAPWAP controller hostname within the configured local domain. The DNS server must resolve that name to the IPv4 or IPv6 address of a suitable wireless controller. DNS discovery can be useful when administrators want centralized controller discovery without configuring controller addresses individually on every AP. It is also useful for APs using static addressing when DHCP Option 43 is unavailable. Correct DNS configuration and reachability must exist before the AP can use this discovery method successfully.

Question 198. What address does an AP use for local Layer 3 broadcast controller discovery

1. 127.0.0.1
2. 224.0.0.1
3. 255.255.255.255
4. 169.254.1.1

Correct Answer: 3. 255.255.255.255

Explanation:

Cisco access points can send a controller discovery request to the IPv4 limited broadcast address 255.255.255.255. Wireless controllers on the same local subnet can respond to the request. Because normal routers do not forward this limited broadcast, the method is useful primarily when the AP and controller are within the same broadcast domain. Distributed deployments normally use methods such as DHCP Option 43, DNS, or static controller configuration when APs must locate controllers across Layer 3 network boundaries.

Question 199. What does static controller configuration on an AP provide

1. A predefined controller address
2. Automatic antenna selection
3. Dynamic channel assignment
4. Guest web authentication

Correct Answer: 1. A predefined controller address

Explanation:

Static controller configuration allows an administrator to specify a preferred wireless controller name and IP address directly on an access point. The AP can then use this stored information during controller discovery rather than depending entirely on DHCP, DNS, or local broadcast discovery. Cisco provides CAPWAP commands for configuring a primary controller entry on the AP. Static configuration can be useful for controlled migrations, branch deployments, or troubleshooting, although it requires more administrative effort than scalable automatic discovery methods when many access points are deployed.

Question 200. What discovery method is unavailable from the Catalyst 9800 internal DHCP server

1. DNS
2. DHCP Option 43
3. Local broadcast
4. AP priming

Correct Answer: 2. DHCP Option 43

Explanation:

Cisco documentation states that the internal DHCP server on the Catalyst 9800 does not support DHCP Option 43 for access point controller discovery. Access points using that DHCP service must therefore locate the controller through another supported mechanism such as local subnet broadcast, DNS resolution, or priming. The internal DHCP service is generally intended for simpler environments such as branches rather than replacing a full external DHCP infrastructure. Designers should verify required DHCP options before deciding to use the controller based internal DHCP service for access point addressing.