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Question 301

A network designer is planning an OSPF network with multiple areas. Which design principle best improves scalability while keeping inter-area routing manageable?

1. Place all routers into Area 0
2. Use Area 0 as the backbone and summarize routes between areas where appropriate
3. Disable SPF calculations on ABRs
4. Redistribute all OSPF routes into BGP

Correct Answer: 2

Explanation

OSPF uses Area 0 as its backbone area, and other areas should connect to it directly or through an appropriate topology. Route summarization at Area Border Routers (ABRs) can significantly reduce the number of inter-area prefixes advertised and limit the impact of topology changes. Putting every router into Area 0 may work for small networks but can reduce scalability as the network grows. Redistributing OSPF into BGP is not required for normal OSPF area scalability. A well-designed hierarchy with a stable backbone and controlled summarization provides better control over routing information and SPF processing.

Question 302

Which BGP attribute is normally used to influence outbound traffic from an autonomous system toward a particular destination?

1. Local Preference
2. MED
3. Origin
4. Next Hop

Correct Answer: 1

Explanation

Local Preference is a BGP path attribute used within an autonomous system to influence which exit point should be selected for outbound traffic. A higher Local Preference value is preferred. Because Local Preference is propagated throughout the internal BGP domain, it is commonly used when an organization has multiple Internet or WAN exit points and wants internal routers to prefer one path over another. MED is generally used to influence inbound traffic from neighboring autonomous systems, although its behavior depends on the network design and policy. Local Preference therefore provides a strong mechanism for controlling outbound path selection.

Question 303

An enterprise needs to carry IPv4 and IPv6 traffic across the same WAN infrastructure during a migration. Which approach provides the most straightforward transition when both protocols are supported end-to-end?

1. IPv4-only tunneling
2. NAT64 only
3. Dual-stack
4. IPv6-only transport

Correct Answer: 3

Explanation

Dual-stack allows network devices and hosts to operate IPv4 and IPv6 simultaneously. This approach is often straightforward when the existing infrastructure can support both protocols because applications can use the protocol they support without requiring translation. IPv4-only tunneling can transport IPv6 over an IPv4 network but does not provide native dual-protocol operation. NAT64 is useful when IPv6-only clients need to access IPv4 services, but it is not a complete replacement for dual-stack during a broad enterprise migration. IPv6-only transport can create compatibility challenges for IPv4 applications and devices. Dual-stack therefore provides a flexible migration model.

Question 304

Which technology is primarily responsible for distributing labels in a traditional MPLS network?

1. PIM
2. LDP
3. DHCP
4. STP

Correct Answer: 2

Explanation

Label Distribution Protocol (LDP) is commonly used in traditional MPLS networks to establish label bindings for IP prefixes. Routers exchange label information so that packets can be forwarded through the MPLS core using labels rather than requiring a complete IP lookup at every hop. LDP typically works alongside an IGP such as OSPF or IS-IS, which provides the underlying reachability information. PIM is associated with IP multicast, DHCP provides address configuration, and STP prevents Layer 2 loops. Modern networks can also use Segment Routing instead of LDP, but LDP remains an important technology in traditional MPLS deployments.

Question 305

A service provider wants to reduce the number of routes advertised from a customer site into the provider network. Which mechanism is most appropriate?

1. Route summarization
2. Increasing BGP keepalive timers
3. Disabling ECMP
4. Increasing interface MTU

Correct Answer: 1

Explanation

Route summarization combines multiple more-specific prefixes into a larger aggregate prefix. When appropriate address planning is used, this can significantly reduce the number of routes advertised between a customer and service provider. Fewer routes reduce routing-table size and can improve scalability. However, summarization must be designed carefully because an overly broad summary can attract traffic toward destinations that are actually unreachable. BGP timers, ECMP, and MTU settings do not reduce the number of advertised prefixes. A network designer should therefore evaluate address allocation, failure behavior, and traffic patterns before implementing aggregation.

Question 306

In an MPLS Traffic Engineering design, what is the primary purpose of explicitly selecting a path for traffic?

1. To replace all routing protocols
2. To force traffic through a desired sequence of links or nodes
3. To eliminate MPLS labels
4. To disable QoS processing

Correct Answer: 2

Explanation

MPLS Traffic Engineering can be used to control how traffic traverses the network rather than relying exclusively on the shortest IGP path. An explicitly selected path can direct traffic through specific links or nodes based on available bandwidth, latency, administrative requirements, or other engineering objectives. This can help avoid congested links and make better use of network capacity. Traffic engineering does not replace the underlying routing architecture and does not eliminate MPLS labels. QoS can also continue to operate alongside traffic engineering. The goal is controlled path selection based on defined network requirements.

Question 307

Which feature of BGP allows multiple equal-cost paths to the same destination to be installed in the routing table?

1. Route Reflector
2. BGP Communities
3. BGP Multipath
4. MED

Correct Answer: 3

Explanation

BGP Multipath allows a router to install multiple eligible BGP paths for the same destination and use them for load sharing. Normally, BGP selects a single best path, even when several paths may have similar characteristics. Multipath requires the paths to meet the platform’s configured eligibility requirements, which can include attributes such as AS-path characteristics, next-hop reachability, and other policy conditions. The exact requirements vary by implementation. Route reflectors improve BGP scalability, communities provide policy signaling, and MED can influence path selection. BGP Multipath is therefore the feature directly associated with using multiple BGP paths simultaneously.

Question 308

A company wants to classify voice traffic before applying QoS treatment. Which action should normally occur first?

1. Classification
2. Congestion avoidance
3. Queue scheduling
4. Packet fragmentation

Correct Answer: 1

Explanation

QoS generally begins with identifying or classifying traffic according to characteristics such as application, protocol, source, destination, DSCP, or other packet information. After classification, traffic can be marked, policed, shaped, queued, or scheduled according to the organization’s policies. For example, voice traffic can be identified and assigned an appropriate DSCP value so downstream devices can recognize its treatment requirements. Congestion-management mechanisms operate after traffic has been identified and assigned to appropriate queues. Fragmentation is not a normal first step in QoS processing. Proper classification is therefore fundamental to implementing an effective end-to-end QoS policy.

Question 309

Which multicast protocol is commonly used by routers to build multicast distribution trees in a sparse-mode environment?

1. FTP
2. PIM
3. LACP
4. BFD

Correct Answer: 2

Explanation

Protocol Independent Multicast (PIM) is widely used to establish multicast forwarding behavior in IP networks. In PIM Sparse Mode, routers initially assume that multicast receivers are sparsely distributed and use a Rendezvous Point (RP) as part of the shared-tree operation. PIM can later transition traffic toward a source-specific shortest-path tree depending on configuration and network behavior. FTP is an application protocol, LACP provides link aggregation, and BFD provides rapid failure detection. A multicast architecture should also consider RP placement, redundancy, receiver distribution, and multicast boundaries when designing a scalable enterprise or service-provider network.

Question 310

What is a major benefit of using BFD alongside a routing protocol?

1. It encrypts routing updates
2. It provides faster detection of forwarding-path failures
3. It assigns IP addresses automatically
4. It replaces the routing protocol database

Correct Answer: 2

Explanation

Bidirectional Forwarding Detection (BFD) provides rapid detection of connectivity failures between neighboring devices. Routing protocols can use relatively conservative hello and dead timers, while BFD can detect failures much more quickly. This allows protocols such as OSPF, BGP, or IS-IS to react sooner when the forwarding path becomes unavailable. BFD does not encrypt routing updates, assign addresses, or replace the routing protocol’s database. When designing BFD, engineers should consider device scale, CPU impact, supported timers, and whether aggressive detection is actually required. It is especially useful for critical links where rapid convergence is important.

Question 311

In a VXLAN deployment, which component typically performs VXLAN encapsulation and decapsulation for attached endpoints?

1. VTEP
2. Route Reflector
3. DHCP Server
4. RADIUS Server

Correct Answer: 1

Explanation

A VXLAN Tunnel Endpoint (VTEP) performs VXLAN encapsulation and decapsulation. When a frame enters the VXLAN overlay from a local endpoint, the VTEP encapsulates it inside a VXLAN/UDP packet and sends it across the IP underlay toward the destination VTEP. The receiving VTEP removes the encapsulation and forwards the original Ethernet frame toward the local endpoint. Route reflectors can distribute control-plane information in EVPN deployments but do not perform the actual VXLAN encapsulation function. DHCP and RADIUS provide different network services. Correct VTEP placement and underlay reachability are essential for reliable VXLAN operation.

Question 312

Which design consideration is particularly important when deploying VXLAN across an IP underlay?

1. Ensuring sufficient MTU for VXLAN encapsulation
2. Disabling all routing protocols
3. Using only Layer 2 switches in the underlay
4. Preventing IP connectivity between VTEPs

Correct Answer: 1

Explanation

VXLAN adds additional headers to the original Ethernet frame, increasing the packet size. If the underlay MTU is not large enough, packets may be fragmented or dropped, depending on the network and configuration. Therefore, designers commonly configure an appropriate jumbo or increased MTU across the VXLAN transport path. The underlay normally uses IP routing and must provide reliable reachability between VTEPs. Preventing VTEP-to-VTEP IP connectivity would break the overlay. Proper MTU planning should cover the entire path, including switches, routers, interfaces, and any intermediate transport network.

Question 313

Which BGP attribute is commonly used inside an autonomous system to indicate the preferred exit point for outbound traffic?

1. MED
2. Local Preference
3. Router ID
4. Originator ID

Correct Answer: 2

Explanation

Local Preference is used within an autonomous system to influence outbound traffic decisions. A higher Local Preference value is normally preferred during BGP best-path selection. For example, an organization with two Internet providers can assign a higher Local Preference to routes learned through its preferred provider. Internal BGP speakers can then select that exit consistently according to policy. MED is primarily intended to communicate a preference for inbound traffic from a neighboring autonomous system. Router ID and Originator ID are identifiers rather than normal outbound traffic-engineering attributes. Local Preference is therefore a key tool for controlling internal exit selection.

Question 314

A network designer needs to prevent a specific set of routes from being advertised to a BGP neighbor. Which policy mechanism is commonly used?

1. Prefix-list with route policy
2. NTP authentication
3. LLDP
4. STP root guard

Correct Answer: 1

Explanation

Prefix lists combined with route policies provide a flexible way to control which prefixes are accepted or advertised through BGP. A prefix list can match specific networks or ranges, while a route map or equivalent policy can apply an action such as permit, deny, attribute modification, or tagging. This allows engineers to implement precise routing policies rather than advertising the entire routing table. NTP authentication protects time synchronization, LLDP provides neighbor information, and STP root guard is a Layer 2 protection mechanism. Route filtering should be carefully tested because incorrect policies can unintentionally remove critical reachability.

Question 315

Which architecture separates the network forwarding infrastructure from the virtual network services that run over it?

1. Underlay and overlay
2. DNS and DHCP
3. LAN and WAN only
4. Access and console

Correct Answer: 1

Explanation

An underlay-and-overlay architecture separates the physical or routed transport network from the logical virtual network built on top of it. The underlay provides IP connectivity between network endpoints such as VTEPs, while the overlay provides virtual connectivity and segmentation independently of the physical topology. VXLAN is a common example of an overlay technology operating over an IP underlay. This separation can simplify network design and improve flexibility because logical networks do not need to directly follow the physical topology. Designers must still ensure the underlay provides adequate reachability, MTU, redundancy, and performance for the overlay.

Question 316

What is the primary purpose of Anycast in a distributed network service design?

1. To make every device use the same MAC address only
2. To allow multiple distributed nodes to advertise the same service address
3. To disable routing convergence
4. To create a single physical network path

Correct Answer: 2

Explanation

Anycast allows multiple geographically or topologically distributed devices to advertise the same IP address or service prefix. Routing then directs a client toward an appropriate reachable instance according to the routing topology. This can improve service availability and provide traffic distribution without requiring the client to know the location of every individual service node. Anycast is commonly used for services such as DNS and can also appear in data-center gateway designs. It does not disable routing or force all traffic onto one physical path. Careful routing and failure-handling design is required so unavailable instances are removed from the routing system.

Question 317

Which mechanism is most useful for protecting a network from a sudden increase in traffic that exceeds the available WAN bandwidth?

1. Traffic shaping
2. DNS recursion
3. ARP inspection only
4. Route summarization

Correct Answer: 1

Explanation

Traffic shaping controls the rate at which traffic is transmitted, helping smooth bursts and match traffic to available bandwidth. On a constrained WAN link, shaping can prevent excessive bursts from overwhelming downstream queues or provider-policing thresholds. It is particularly useful when the service provider specifies a committed bandwidth rate. Route summarization affects routing-table size rather than packet transmission rate. DNS recursion handles name resolution, and ARP inspection addresses Layer 2 security concerns. A complete QoS design may combine shaping with classification, marking, queuing, and policing depending on the service requirements and traffic patterns.

Question 318

In a data center using EVPN multihoming, what is a key benefit of connecting an endpoint to multiple VTEPs?

1. Removal of all routing protocols
2. Increased endpoint redundancy and multihoming resilience
3. Elimination of IP addressing
4. Mandatory single-link forwarding

Correct Answer: 2

Explanation

EVPN multihoming allows an Ethernet segment or endpoint to connect to multiple network devices, providing redundancy and improved availability. If one VTEP or physical connection fails, traffic can continue through the remaining multihoming peer according to the design. EVPN provides control-plane mechanisms that help coordinate Ethernet-segment information and forwarding behavior. This avoids relying solely on traditional Layer 2 mechanisms for redundancy. Multihoming does not eliminate IP addressing or routing protocols, and it does not require traffic to use only one physical link. Designers should also consider load balancing, failure detection, convergence, and loop prevention.

Question 319

Which network monitoring approach provides a continuous stream of operational data from network devices instead of relying only on periodic polling?

1. Streaming telemetry
2. Static routing
3. NAT overload
4. Port security

Correct Answer: 1

Explanation

Streaming telemetry allows network devices to continuously send selected operational and performance information to monitoring or analytics systems. Compared with traditional periodic polling, streaming telemetry can provide more frequent and near-real-time visibility into metrics such as interface counters, CPU utilization, queue statistics, routing state, and environmental information. This can support faster detection of performance issues and automated operational workflows. Static routing, NAT overload, and port security address different network functions. When designing telemetry, engineers should consider data volume, collection intervals, transport security, storage requirements, and which metrics are actually useful for operational decisions.

Question 320

A company wants to connect its data center to multiple cloud providers while maintaining consistent routing and security policies. Which design principle is most important?

1. Build independent connections without common policy controls
2. Use centralized or consistently enforced routing and security policy across cloud connections
3. Disable dynamic routing everywhere
4. Place all cloud traffic on a single unmanaged Internet connection

Correct Answer: 2

Explanation

Multi-cloud connectivity becomes easier to operate when routing, security, segmentation, and traffic-engineering policies are applied consistently across cloud connections. Depending on the architecture, organizations may use dedicated connectivity, SD-WAN, cloud exchange services, VPNs, or combinations of these technologies. A common policy framework helps control which networks can communicate, how routes are exchanged, and where security inspection occurs. Completely independent connections can create inconsistent behavior and operational complexity. A single unmanaged Internet path also introduces a significant dependency. The final architecture should consider availability, latency, bandwidth, security requirements, cloud-native capabilities, and failure scenarios.