Cisco 350-401 Implementing Cisco Enterprise Network Core Technologies (ENCOR) Exam Dumps and Practice Test Questions Set 14 Q196-210
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Question 196:
Which wireless feature helps reduce channel interference in high-density Cisco WLAN deployments by automatically adjusting power and channel settings across access points?
DTIM
B. RRM
C. RxSOP
D. MU-MIMO
Correct Answer: B
Explanation:
DTIM is a Delivery Traffic Indication Message used in wireless networks to inform sleeping clients about buffered broadcast and multicast traffic. Although it plays an important role in power-saving mechanisms, it does not help in reducing channel interference or optimizing RF performance in high-density environments. DTIM focuses solely on client-side power conservation and does not involve channel assignment, transmit power control, or access-point coordination. Therefore, it is not the correct solution for controlling interference.
RxSOP (Receiver Start of Packet) is primarily used to adjust the sensitivity threshold of access points. By increasing the RxSOP threshold, APs become less sensitive to distant or weak signals, improving client roaming and reducing sticky client behavior. However, RxSOP does not automatically adjust RF parameters such as channels or transmit power across multiple APs. It also requires manual tuning and does not coordinate AP behavior system-wide, which limits its ability to systematically reduce interference.
MU-MIMO allows an 802.11ac Wave 2 or 802.11ax access point to transmit data streams to multiple clients simultaneously. This increases spectrum efficiency and overall throughput but does not reduce channel interference or dynamically optimize frequency usage. MU-MIMO focuses on increasing capacity on a single AP rather than managing channel or power settings across the entire wireless deployment.
The correct answer is RRM, Cisco Radio Resource Management. RRM automatically manages channel assignments, power settings, coverage hole detection, and neighbor analysis in a Cisco wireless network. It continuously evaluates RF conditions, including interference levels, AP density, and noise, and then automatically adjusts parameters to optimize coverage and reduce co-channel interference. RRM uses algorithms such as DCA (Dynamic Channel Assignment), TPC (Transmit Power Control), and CHD (Coverage Hole Detection) to maintain an optimal RF environment across the entire network. This ensures APs operate on the best possible channels with appropriately balanced transmit power. In high-density deployments, RRM is essential for maintaining efficient RF performance and minimizing interference, which directly improves client connectivity and overall WLAN stability. Therefore, RRM is the only feature among the four capable of performing automatic RF optimization at the system level.
Question 197:
Which routing protocol uses the DUAL algorithm to ensure loop-free paths and rapid convergence?
OSPF
B. RIPv2
C. EIGRP
D. IS-IS
Correct Answer: C
Explanation:
In the world of routing protocols, understanding the mechanisms that govern path selection, convergence, and loop prevention is crucial for designing efficient and reliable networks. Among the many routing protocols available, only a select few incorporate advanced algorithms to ensure both rapid convergence and loop-free operation. One such algorithm is the Diffusing Update Algorithm, commonly known as DUAL. Identifying which protocols utilize DUAL and which rely on alternative methods is essential for network engineers and architects.
OSPF, or Open Shortest Path First, is a widely deployed link-state routing protocol known for its scalability and fast convergence. OSPF constructs a comprehensive map of the network by exchanging link-state advertisements between routers. Using this information, OSPF runs the Shortest Path First (SPF) algorithm, which calculates a complete tree of all possible paths from the router to every destination within the network. While OSPF is effective in quickly adapting to network changes and provides a hierarchical design through the use of areas, it does not implement DUAL. SPF focuses on building the shortest path tree without considering feasible successors or the loop-free guarantees that DUAL provides. Therefore, despite its efficiency and robustness, OSPF cannot be classified as a protocol that employs DUAL.
RIPv2, another commonly used protocol, operates differently. It is a distance-vector protocol that determines the best path based on hop count and relies on the Bellman-Ford algorithm for route calculation. RIPv2 is relatively simple to implement but lacks the advanced loop-avoidance mechanisms found in more modern protocols. Its convergence relies heavily on timers such as update intervals, invalid, and hold-down timers, which makes it significantly slower in reacting to network changes compared to protocols with DUAL. Additionally, RIPv2 does not maintain feasible successors or provide instantaneous failover, as DUAL does. For these reasons, RIPv2 does not meet the criteria for protocols that utilize the Diffusing Update Algorithm.
IS-IS, or Intermediate System to Intermediate System, is another link-state protocol similar to OSPF but designed with a different internal structure, often seen in service provider networks. IS-IS exchanges Link State Packets (LSPs) and uses Type-Length-Value (TLV) structures to communicate routing information. It also employs a two-level hierarchical design, offering scalability and robustness. Like OSPF, IS-IS relies on the SPF algorithm to determine the shortest paths to all destinations. It does not, however, implement DUAL, nor does it maintain feasible successors or provide loop-free backup paths in the same manner. Its convergence is dependent on recalculating the SPF tree when network changes occur.
EIGRP, or Enhanced Interior Gateway Routing Protocol, stands apart from these protocols due to its unique integration of the Diffusing Update Algorithm. DUAL allows EIGRP to maintain loop-free paths by using feasible successors and applying the feasibility condition, ensuring alternative routes are safe before being installed in the routing table. This capability enables rapid convergence, as EIGRP can immediately switch to a backup route without triggering network instability. When no feasible successor exists, DUAL performs a controlled query process to find a loop-free path, maintaining network stability throughout the process. EIGRP’s combination of multiple backup paths, a composite metric, and DUAL’s loop-free guarantees makes it uniquely capable among routing protocols.
While OSPF, RIPv2, and IS-IS are powerful and widely used routing protocols, none of them utilize the Diffusing Update Algorithm. Only EIGRP leverages DUAL, offering fast, loop-free convergence with multiple backup routes, which is why it is the sole protocol in this category.
Question 198:
Which mechanism does Cisco DNA Center use to automate policy enforcement across a Software-Defined Access (SD-Access) fabric?
DNAC Assurance
B. LISP
C. Cisco ISE with Scalable Group Tags
D. NetFlow
Correct Answer: C
Explanation:
DNAC Assurance focuses on monitoring, analytics, client troubleshooting, and performance insights. It does not enforce policies across the SD-Access fabric. While it provides health scores and diagnostic reports, it is not responsible for applying or propagating security segmentation policies or fabric-level access control.
LISP (Locator/ID Separation Protocol) serves as the control-plane mechanism within SD-Access. It maps endpoints to their locations using EID-to-RLOC mappings. LISP is critical for endpoint mobility, simplified routing, and fabric forwarding. However, LISP does not enforce security policies or access control rules. It merely separates identifiers from locators and directs traffic appropriately.
NetFlow is a traffic analysis and monitoring technology. It gathers flow data for performance monitoring, capacity planning, or anomaly detection. Although useful for visibility, NetFlow does not apply access policies or segment the network.
The correct answer is Cisco ISE with Scalable Group Tags (SGTs). In SD-Access, Cisco DNA Center integrates with Cisco ISE to define identity-based policies. These policies use SGTs, which tag users and devices based on their identity and assigned role. The SD-Access fabric then applies these tags consistently across the network through the Cisco TrustSec architecture. Policies follow endpoints throughout the network, enabling consistent segmentation and secure access regardless of location. DNA Center automates the provisioning and propagation of these SGT-based policies. Thus, ISE with SGTs is the mechanism that enforces policy across the fabric.
Question 199:
Which WAN architecture allows dynamic path selection and application-aware routing across multiple transport links?
IPsec VPN
B. SD-WAN
C. GRE Tunneling
D. MPLS L2VPN
Correct Answer: B
Explanation:
In modern enterprise networking, ensuring secure and efficient communication between branch offices, data centers, and cloud environments is critical. Several technologies are available to connect these sites, each with its own strengths and limitations. Understanding the differences between IPsec VPN, GRE tunneling, MPLS L2VPN, and SD-WAN is essential when choosing the right solution for dynamic, application-driven environments.
IPsec VPN is one of the most widely used methods for secure connectivity over the internet. It establishes encrypted tunnels between endpoints, ensuring that data is protected from eavesdropping and tampering. While IPsec VPN excels at security, its functionality is limited when it comes to intelligent network management. Specifically, it does not provide application-aware routing or dynamic path selection. An IPsec VPN tunnel simply transmits traffic over a predetermined path, without evaluating the real-time performance of available links. Because it lacks mechanisms to monitor metrics such as latency, jitter, or packet loss, it cannot automatically select the most efficient route for individual applications. This static behavior can result in suboptimal performance, particularly for latency-sensitive or high-priority applications.
GRE tunneling, or Generic Routing Encapsulation, is another common method used to transport data across networks. GRE allows encapsulation of various network layer protocols, including non-IP traffic, making it flexible for certain scenarios. However, like IPsec, GRE does not include the intelligence needed for modern application-driven networks. Traffic routing decisions must be configured manually, and GRE tunnels do not perform continuous monitoring of link quality. There is no mechanism for prioritizing specific applications or dynamically adjusting routes based on network conditions. As a result, while GRE is useful for protocol compatibility and simple tunneling needs, it falls short in delivering optimized performance across multiple links.
MPLS L2VPN, which provides Layer-2 virtual circuits over an MPLS backbone, offers predictable performance and high-quality service. It enables point-to-point or multipoint connectivity with defined service levels, which is valuable for organizations requiring stable and reliable bandwidth. However, MPLS L2VPN lacks the dynamic application routing and real-time WAN optimization capabilities found in more advanced solutions. It does not make routing decisions based on application type, current network conditions, or business intent. Network administrators must still rely on static configurations and manual adjustments to manage performance and avoid congestion, limiting its flexibility in multi-link, cloud-driven environments.
By contrast, SD-WAN is designed to overcome these limitations and provide a more intelligent, application-aware approach to WAN connectivity. SD-WAN continuously measures key network performance indicators, including latency, jitter, and packet loss, across all available links such as MPLS, broadband, or LTE. Using these measurements, SD-WAN can dynamically select the optimal path for each application, ensuring that critical services receive the best possible performance. Centralized policy management allows organizations to define traffic priorities based on business intent, while features such as segmentation and application-aware routing improve both security and efficiency. This combination of real-time monitoring, dynamic path selection, and policy-driven traffic control makes SD-WAN the most suitable choice for modern enterprise networks that demand both performance and flexibility.
While IPsec VPN, GRE, and MPLS L2VPN provide secure and reliable connectivity, they lack the dynamic routing and intelligent traffic management capabilities required for today’s application-centric networks. SD-WAN addresses these gaps by continuously monitoring link performance, selecting the best paths, and applying centralized, business-driven policies, making it the optimal solution for modern WAN environments.
Question 200:
Which QoS tool is used to prevent congestion by selectively dropping packets before a queue becomes full?
Traffic Shaping
B. Policing
C. WRED
D. Priority Queuing
Correct Answer: C
Explanation:
Traffic management in networking involves several techniques to ensure efficient data flow, prevent congestion, and maintain the quality of service. One common method is traffic shaping. Traffic shaping works by regulating the rate at which packets are transmitted from a device, delaying some packets if necessary to conform to a pre-defined bandwidth limit. This approach is particularly useful for smoothing out bursty traffic, as it temporarily stores excess packets in a buffer and releases them gradually, rather than sending them all at once. By controlling the outbound flow, traffic shaping can create a more predictable and stable network experience. However, it is important to note that traffic shaping does not prevent congestion through selective packet dropping. Its primary function is to delay packets to match the configured rate, not to manage the state of the network queues dynamically or prevent potential overflows.
In contrast, traffic policing is designed to enforce strict limits on traffic rates. When traffic exceeds the configured threshold, policing responds by either dropping the excess packets or marking them for lower priority handling. Unlike shaping, policing does not attempt to smooth bursts or buffer traffic; it reacts immediately when the rate limit is exceeded. This can lead to packet loss and, in the case of TCP traffic, trigger retransmissions as the sender is forced to slow down and resend lost packets. Policing operates without using congestion avoidance techniques, and it does not differentiate based on the depth of queues or other dynamic network conditions. Its function is purely rate enforcement, not congestion management.
Priority queuing represents another approach to managing network traffic. In this method, certain traffic classes are assigned absolute priority, ensuring that high-priority packets are transmitted before lower-priority traffic. While this guarantees that critical traffic is delivered promptly, it does not actively mitigate congestion or prevent queue overflow. Lower-priority traffic may experience delays or even starvation if higher-priority traffic dominates the queue. Priority queuing focuses solely on the ordering of packet transmission rather than managing overall congestion or balancing traffic across the network.
The most effective method for congestion avoidance in scenarios where queue management is critical is Weighted Random Early Detection, or WRED. WRED operates by continuously monitoring the depth of a queue and probabilistically dropping packets before the queue reaches its maximum capacity. This early packet dropping sends signals to TCP senders, prompting them to slow down their transmission rate before congestion becomes severe. By taking action prior to queue overflow, WRED helps maintain queue stability and prevents the phenomenon known as congestion collapse, which can occur when multiple senders simultaneously react to packet loss. Unlike traffic shaping, policing, or simple priority queuing, WRED is a proactive mechanism that dynamically adjusts to network conditions and aims to prevent congestion rather than merely react to it.
While traffic shaping delays packets to smooth bursts, policing strictly enforces rate limits by dropping excess packets, and priority queuing ensures certain traffic is sent first, WRED stands out as a sophisticated congestion-avoidance technique. By dropping packets probabilistically based on queue occupancy, it signals senders to adjust their rate, stabilizing the network and preventing severe congestion before it occurs. For networks where maintaining queue stability and avoiding congestion collapse is crucial, WRED provides the most effective solution.
Question 201
Which Cisco SD-Access component acts as the control-plane node responsible for maintaining the endpoint ID-to-location mapping database?
A) LISP
B) VXLAN
C) DNA Center
D) IS-IS
Answer: A) LISP
Explanation:
In SD-Access architectures, VXLAN is primarily responsible for data-plane encapsulation, allowing user traffic to be carried across the fabric. It wraps the original packets with a VXLAN header so they can traverse the network efficiently and be delivered to the correct destination fabric node. While VXLAN enables seamless transport of traffic across the SD-Access fabric, it does not handle any control-plane functions, such as tracking the identities of endpoints or maintaining mappings between users and their associated fabric locations. Essentially, VXLAN focuses solely on the encapsulation and delivery of packets rather than on understanding or managing endpoint identity within the network.
Similarly, DNA Center plays a central role in the management and orchestration of SD-Access deployments. It provides a comprehensive platform for network provisioning, automation, monitoring, and policy enforcement. Through DNA Center, administrators can design and apply network policies, monitor fabric health, and automate configuration tasks. Despite these powerful management capabilities, DNA Center does not perform the actual control-plane functions necessary to maintain real-time mappings of endpoints to specific fabric locations. Its role is largely supervisory and administrative, enabling consistent configuration and visibility rather than providing the mechanisms for endpoint resolution.
IS-IS, as the interior gateway protocol used in SD-Access underlays, is responsible for establishing IP-level connectivity among fabric nodes. It ensures that all nodes within the fabric are reachable by exchanging routing information, maintaining network topology awareness, and providing a foundation for traffic forwarding. However, IS-IS does not manage endpoint identities or track their locations within the fabric. Its scope is limited to node-to-node reachability, leaving the resolution of user or device locations to a dedicated control-plane protocol.
The control-plane responsibilities in SD-Access are fulfilled by LISP, or Locator/ID Separation Protocol. LISP is tasked with maintaining mappings between Endpoint Identifiers (EIDs) and Routing Locators (RLOCs). EIDs represent the identity of an endpoint, such as a user device, while RLOCs indicate the physical or logical fabric node where the endpoint is connected. When an endpoint joins the network, it registers its EID and corresponding RLOC to the control-plane node using LISP. This registration enables the fabric to know precisely where each endpoint resides.
When traffic needs to be forwarded to a particular endpoint, LISP provides the necessary mapping information so that the fabric edge nodes can deliver packets accurately to the correct location. This capability is critical for ensuring seamless mobility of endpoints within the fabric, allowing users to move across different network segments without losing connectivity or policy enforcement. LISP’s mapping system also supports scalable network designs by decoupling endpoint identity from location, enabling the fabric to grow without introducing complexity or requiring manual configuration of every node.
while VXLAN handles data encapsulation, DNA Center provides management and orchestration, and IS-IS ensures underlay routing, LISP is the essential control-plane protocol that tracks endpoints and resolves their locations in the SD-Access fabric. Its mapping of EIDs to RLOCs is fundamental for mobility, policy enforcement, and scalable endpoint tracking. Therefore, LISP is the correct answer because it delivers the core functionality needed to identify, track, and locate endpoints across the network fabric, enabling SD-Access to operate efficiently and reliably.
Question 202
Which QoS mechanism classifies and marks packets at the moment they enter the network, determining how they will be treated throughout the forwarding path?
A) Policing
B) Marking
C) Shaping
D) Queuing
Answer: B) Marking
Explanation:
Queuing is another integral part of QoS. It determines the order in which packets are forwarded during periods of congestion, deciding which packets are transmitted first, which are held temporarily, and which may be dropped if resources are limited. Queuing mechanisms, such as priority queuing, weighted fair queuing, and low-latency queuing, ensure that high-priority traffic like voice or video experiences minimal delay while less time-sensitive traffic waits its turn. However, queuing does not inherently classify traffic or assign priority levels—it relies on markings that have already been applied to packets to make forwarding decisions. Without proper classification and marking at the network edge, queuing alone cannot guarantee that critical applications receive the treatment they require.
Marking is the process that occurs at the network edge, where packets are assigned specific Quality of Service values such as Differentiated Services Code Point (DSCP) or Class of Service (CoS). By assigning these values early, marking establishes the priority and handling rules for each packet as it traverses the network. These markings provide a consistent reference for all subsequent QoS mechanisms, including policing, shaping, and queuing, ensuring that packets are treated according to their priority regardless of where congestion or other network events occur. Marking is especially important in enterprise networks where delay-sensitive applications, such as voice over IP (VoIP) or video conferencing, must be delivered reliably and with minimal latency.
By classifying and marking packets at the point of entry, administrators can ensure that high-priority traffic receives preferential treatment throughout the network, while lower-priority traffic is handled appropriately without impacting critical applications. This proactive classification enables end-to-end QoS enforcement, allowing enterprises to maintain optimal performance, prevent congestion-related issues, and provide a consistent experience for users and applications.
While policing, shaping, and queuing each play essential roles in controlling and managing traffic, they all rely on the initial markings assigned to packets. Marking is the foundational step that identifies the type of traffic and dictates how it should be treated across the entire network. Without proper marking, QoS policies cannot function effectively, and critical applications may suffer from delay, jitter, or packet loss. Therefore, marking is the primary mechanism responsible for classifying traffic upon entry and establishing the basis for all subsequent QoS decisions, making it indispensable in any enterprise network that prioritizes reliability and performance.
The correct answer is marking because it sets the priority for traffic from the outset, guiding how all packets are handled end-to-end and ensuring that network resources are allocated according to business-critical needs.
Question 203
Which routing protocol uses areas to optimize network scaling and reduces SPF calculations by limiting topology flooding to specific segments?
A) OSPF
B) RIP
C) EIGRP
D) BGP
Answer: A) OSPF
Explanation:
Routing protocols are essential for determining the paths that data takes across a network, but not all protocols handle scalability and network complexity in the same way. One key differentiator among these protocols is the use of areas, which allows a network to be segmented logically to improve efficiency and reduce unnecessary processing. Among the common protocols—RIP, EIGRP, BGP, and OSPF—only one leverages this concept of areas to optimize routing operations and maintain scalability: OSPF.
RIP, or Routing Information Protocol, is a classic distance-vector protocol that uses hop count as its primary metric to determine the best path to a destination. While RIP is simple and easy to configure, it has notable limitations. It supports a maximum hop count of 15, making it unsuitable for larger networks. Additionally, RIP does not use areas or hierarchical segmentation to optimize routing updates. When network changes occur, RIP relies on periodic full routing table exchanges, which can lead to slow convergence and inefficient bandwidth utilization, particularly in more complex topologies.
EIGRP, or Enhanced Interior Gateway Routing Protocol, is a Cisco-developed protocol often described as a hybrid between distance-vector and link-state approaches. It converges quickly and considers multiple metrics such as bandwidth, delay, and reliability when calculating paths. EIGRP uses the concept of autonomous systems to group routers for administrative purposes, but it does not employ areas to limit the scope of routing updates or to reduce computational overhead. While EIGRP is highly efficient within its operational scope, it lacks the hierarchical structure that OSPF provides, which can be critical for very large networks.
BGP, or Border Gateway Protocol, is primarily an exterior gateway protocol designed for routing between autonomous systems across the Internet. BGP relies on path-vector mechanisms and policies rather than traditional metrics like hop count or cost. It does not divide networks into areas and instead focuses on exchanging reachability information between different administrative domains. While BGP excels at inter-domain routing and policy control, it does not provide mechanisms for internal area-based optimization.
OSPF, or Open Shortest Path First, is a link-state routing protocol that addresses the scalability challenges inherent in large networks by introducing the concept of areas. In OSPF, the network is divided into multiple areas to limit the propagation of link-state updates. Each area maintains its own topology and SPF (Shortest Path First) calculations, while the backbone area, known as area 0, provides the central hub for inter-area communication. By containing most routing changes within their respective areas, OSPF significantly reduces the amount of processing required for SPF recalculations and minimizes network-wide flooding of updates. This hierarchical design enables OSPF to scale efficiently, maintain faster convergence in large topologies, and provide predictable and manageable routing behavior.
The use of areas is fundamental to OSPF’s ability to support large enterprise networks, as it balances the need for rapid convergence with efficient resource utilization. By structuring the network hierarchically and isolating routing calculations to specific regions, OSPF improves performance, reduces computational load, and ensures that local network changes do not trigger unnecessary global recalculations.
Therefore, the correct choice is OSPF. Its area-based architecture allows for scalable routing, efficient update propagation, and reduced computational overhead, making it the preferred protocol for large and complex network environments.
Question 204
Which wireless feature ensures that APs adjust their transmit power automatically to prevent coverage holes and reduce co-channel interference?
A) RRM
B) WPA3
C) 802.11i
D) DTIM
Answer: A) RRM
Explanation:
In wireless networking, several technologies contribute to performance, security, and stability, but not all of them influence the behavior of radio frequencies. When evaluating which feature automatically adjusts transmit power and manages channel assignments, it is important to distinguish between protocols focused on security, timing, and RF optimization. Only one of the listed technologies is designed specifically to fine-tune wireless radio operations, and that is Radio Resource Management.
WPA3 represents the latest generation of Wi-Fi security standards. Its primary purpose is to strengthen protection for wireless communications through more advanced authentication mechanisms and encryption. It introduces features such as individualized data encryption and enhanced protections against brute-force attacks, improving confidentiality for users and devices. While WPA3 greatly enhances overall network security, its scope does not extend to controlling radio channels, adjusting transmit power, or optimizing RF conditions.
The 802.11i amendment, which underpins modern Wi-Fi security standards such as WPA2, focuses entirely on encryption and key management. It defines how wireless networks authenticate clients and how data is securely exchanged. This includes mechanisms such as the four-way handshake, the use of AES encryption, and the improvement of overall security architecture. Like WPA3, however, 802.11i is centered on safeguarding data rather than managing radio characteristics or automatically responding to changing RF environments.
DTIM, or Delivery Traffic Indication Message, serves an important role in the timing of broadcast and multicast frame delivery. It tells wireless clients when buffered multicast or broadcast traffic will be sent, helping conserve battery life on mobile devices and ensuring predictable transmission behavior. Although DTIM is essential for power-saving features and efficient delivery scheduling, it has no influence on channel selection, interference mitigation, or power adjustment within an access point.
Radio Resource Management stands apart because it is designed specifically to optimize wireless performance by dynamically controlling RF parameters. RRM evaluates the surrounding radio environment, including interference levels, channel congestion, and neighboring access point power settings. Based on this continuous assessment, it automatically tunes access point transmit power to maintain consistent coverage and avoid signal overlap that can lead to co-channel interference. It also adjusts channel assignments to distribute wireless traffic across cleaner, less congested channels, improving overall performance and stability.
By actively monitoring the RF environment and making automatic adjustments, RRM helps maintain a balanced wireless infrastructure. It identifies coverage gaps, mitigates excessive signal overlap, and ensures access points operate on optimal settings as conditions change throughout the day. This automation reduces manual tuning by network administrators and contributes significantly to smoother connectivity and better wireless efficiency in enterprise deployments.
For these reasons, RRM is the correct choice. It is the only feature among the options that dynamically manages radio behavior, adjusting both power levels and channel assignments to optimize wireless performance and ensure a stable, interference-aware network environment.
Question 205
Which network virtualization technology allows multiple isolated logical routers to exist within a single physical router chassis?
A) VRF
B) HSRP
C) LACP
D) STP
Answer: A) VRF
Explanation:
In modern enterprise networks, different technologies serve distinct purposes, and understanding their roles is essential when determining which one supports routing table virtualization. Some protocols provide redundancy, others focus on link aggregation or loop prevention, but only one enables the creation of completely separate routing environments on the same physical device. That technology is Virtual Routing and Forwarding, commonly known as VRF.
Hot Standby Router Protocol (HSRP) is often deployed to ensure default gateway redundancy. It allows multiple routers to share a virtual IP address that end hosts use as their gateway. One router operates as the active gateway while another functions as a standby, ready to take over if the active router fails. This capability increases network reliability, but HSRP does not influence how routing tables are structured or shared. It does not create isolation between routing domains; instead, it focuses solely on gateway failover and ensuring continuous availability.
Link Aggregation Control Protocol (LACP) serves a different purpose. It allows multiple physical links between devices to be combined into one logical connection. This aggregation improves both bandwidth and redundancy, offering increased throughput and resiliency. However, LACP is confined to link-layer operations and does not interact with IP routing tables, forwarding decisions, or network segmentation at the Layer 3 level. It cannot divide routing information or create separate logical routing environments.
Spanning Tree Protocol (STP) is designed to address the problem of loops in Layer 2 Ethernet networks. In environments with redundant paths, loops can cause broadcast storms and network instability. STP resolves this by calculating a loop-free topology and blocking redundant paths as needed. Although STP plays a vital role in maintaining network stability, it has no function related to routing or the creation of isolated forwarding instances. It operates entirely at Layer 2 and has no impact on Layer 3 routing behavior.
VRF, on the other hand, is specifically designed to create multiple, independent routing instances on the same physical device. Each VRF maintains its own separate routing table, forwarding decisions, and interface associations. This allows different customer networks, departments, or application environments to run in complete isolation while sharing the same router or switch hardware. Traffic from one VRF never interacts with traffic from another unless explicitly configured to do so through mechanisms such as route leaking. This level of separation is crucial in environments such as service provider networks, multi-tenant data centers, and large enterprises that need strict segmentation for security, compliance, or organizational reasons.
By virtualizing routing tables, VRF enables a single piece of hardware to behave as though it is multiple routers operating independently. This provides tremendous flexibility and scalability, allowing networks to consolidate infrastructure while retaining strong segmentation. It also supports overlapping IP address spaces, something impossible without routing isolation.
For these reasons, VRF is the correct choice when the requirement is routing table virtualization. It delivers the isolation, flexibility, and control needed to operate multiple logical networks within the same physical device, something HSRP, LACP, and STP are not designed to accomplish.
Question 206
Which routing protocol uses the Bellman-Ford algorithm and a maximum hop count of 15, making it suitable only for small networks?
A) RIP
B) OSPF
C) EIGRP
D) IS-IS
Answer: A) RIP
Explanation:
OSPF is a link-state routing protocol that uses the SPF (Shortest Path First) algorithm to compute routes. It does not have a hop-count limitation and is suitable for medium to large networks due to its hierarchical area design. EIGRP is an advanced distance-vector protocol that uses the DUAL algorithm for loop-free and fast convergence. It supports a much larger network size and does not rely on hop counts as a limiting factor. IS-IS is also a link-state protocol and uses SPF to compute optimal paths. It is highly scalable and used in large service provider networks.
RIP, or Routing Information Protocol, is a simple distance-vector routing protocol. It calculates the best path based on hop count, which is the number of routers a packet must traverse. RIP defines 15 hops as the maximum, making any network beyond that unreachable. RIP periodically advertises its entire routing table every 30 seconds, which can lead to slow convergence and increased network traffic in larger networks. Because of its simplicity and limitations, RIP is primarily suited for small networks where simplicity is preferred over scalability.
Therefore, the correct answer is RIP because it uses the Bellman-Ford algorithm, relies on hop count for path selection, and is appropriate only for small-scale network topologies.
Question 207
Which QoS mechanism delays traffic to conform to a specified rate, smoothing bursts and preventing congestion downstream?
A) Policing
B) Shaping
C) WRED
D) Priority Queuing
Answer: B) Shaping
Explanation:
Policing enforces a traffic rate by dropping or remarking packets that exceed a configured bandwidth limit. It does not delay or buffer excess traffic, so it can lead to immediate packet loss. WRED (Weighted Random Early Detection) is a congestion-avoidance mechanism that selectively drops packets before a queue is full to prevent congestion collapse. Priority Queuing always forwards high-priority traffic first, which can starve lower-priority traffic but does not smooth bursts.
Traffic shaping, in contrast, buffers excess packets and schedules them for later transmission to ensure the outgoing traffic conforms to a specified rate. By controlling the traffic flow, shaping smooths out bursts, prevents sudden congestion on downstream links, and helps maintain QoS for sensitive applications like voice and video. Shaping is often applied at the network edge to control traffic before it enters the core or WAN. It works closely with queuing and marking mechanisms to enforce consistent treatment of traffic across the network.
Therefore, the correct answer is Shaping because it delays packets to conform to a defined rate, smooths bursts, and helps prevent downstream congestion.
Question 208
Which IPv6 address type is shared by multiple devices but delivers packets to the nearest device, commonly used for redundant services?
A) Unicast
B) Multicast
C) Anycast
D) Link-local
Answer: C) Anycast
Explanation:
Unicast addresses are unique to a single interface and deliver packets only to that device. Multicast addresses deliver packets to all devices subscribed to a group, supporting one-to-many communication, but do not differentiate based on distance. Link-local addresses are automatically assigned to interfaces for communication within the local subnet and are not routable beyond the link.
Anycast addresses are assigned to multiple devices, and packets sent to an anycast address are delivered to the nearest device, based on routing metrics. This is commonly used for redundant services such as DNS or content delivery networks, where the nearest server should respond to reduce latency. Anycast provides scalability, load balancing, and high availability by allowing multiple devices to share the same IP while still delivering traffic efficiently.
Therefore, the correct answer is Anycast because it delivers traffic to the nearest of multiple devices sharing the same address, supporting redundancy and optimized routing.
Question 209
Which WAN technology allows multiple transport links to be combined and managed dynamically based on application performance and business intent?
A) IPsec VPN
B) SD-WAN
C) MPLS L2VPN
D) GRE Tunnel
Answer: B) SD-WAN
Explanation:
IPsec VPN provides encryption and secure tunnels but does not offer application-aware routing or dynamic path selection. MPLS L2VPN offers point-to-point or multipoint Layer 2 connectivity, providing QoS and reliability, but it does not manage multiple transport links dynamically. GRE tunnels provide encapsulation for various protocols over IP but are static and require manual configuration without dynamic path selection.
SD-WAN allows multiple WAN links, such as MPLS, broadband, and LTE, to be managed dynamically. It monitors real-time performance metrics such as latency, jitter, and packet loss and directs application traffic over the best-performing path based on business and application policies. SD-WAN improves WAN efficiency, ensures SLA compliance for critical applications, and provides centralized management, segmentation, and visibility. By dynamically selecting optimal paths, SD-WAN enhances reliability, performance, and cost-effectiveness in enterprise WAN deployments.
Therefore, the correct answer is SD-WAN because it enables dynamic path selection, application-aware routing, and centralized management across multiple transport links.
Question 210
Which Cisco wireless protocol automatically adjusts channels and transmit power across APs to optimize RF performance and reduce interference?
A) 802.11r
B) RRM
C) DTIM
D) MU-MIMO
Answer: B) RRM
Explanation:
802.11r facilitates fast roaming by pre-establishing security keys but does not control RF channel selection or power. DTIM defines intervals for notifying sleeping clients about buffered broadcast and multicast traffic, with no impact on channel assignment or transmit power. MU-MIMO enables an AP to transmit to multiple clients simultaneously, increasing throughput, but it does not optimize channels or reduce interference across the WLAN.
RRM (Radio Resource Management) continuously monitors the RF environment and dynamically adjusts channels and transmit power for all APs in the network. Its goals are to minimize co-channel interference, prevent coverage holes, and maintain consistent wireless performance in high-density environments. RRM uses algorithms such as Dynamic Channel Assignment (DCA) and Transmit Power Control (TPC) to ensure optimal RF coverage and capacity, automatically adapting to environmental changes, interference, and device density. This automation reduces manual RF planning and improves client experience.
Therefore, the correct answer is RRM because it automatically manages RF channels and power to optimize performance and minimize interference.