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Question 341

A service provider wants to prevent one customer from receiving routes belonging to another VPN. Which MPLS VPN mechanism provides this separation?

1. Route Target
2. Spanning Tree
3. LACP
4. BFD

Correct Answer: 1

Explanation

Route Targets (RTs) are extended BGP communities used in MPLS Layer 3 VPNs to control which VPN routes are imported into or exported from a VRF. By assigning appropriate RTs, a provider can ensure that routes belonging to one customer are not automatically imported into another customer’s VRF. Route Distinguishers provide uniqueness for overlapping prefixes but do not themselves define import/export policy. LACP provides link aggregation, BFD provides fast failure detection, and Spanning Tree operates at Layer 2. Correct RT planning is therefore essential for customer isolation and controlled route sharing.

Question 342

Which technology allows IPv4 and IPv6 networks to coexist while applications gradually transition to IPv6?

1. IPv6-only networking
2. Dual-stack
3. MPLS LDP
4. VLAN trunking

Correct Answer: 2

Explanation

Dual-stack allows network devices and hosts to operate IPv4 and IPv6 simultaneously. This provides a flexible migration strategy because applications can continue using IPv4 while IPv6 connectivity is introduced incrementally. Devices can select the appropriate protocol based on application and destination requirements. IPv6-only designs may require translation or proxy mechanisms for IPv4-only applications. MPLS LDP is a label-distribution mechanism, while VLAN trunking carries multiple Layer 2 VLANs over a link. A successful dual-stack deployment requires IPv6 addressing, routing, security policies, DNS support, monitoring, and appropriate device capability.

Question 343

Which BGP feature can be used to attach additional policy information to routes without changing the destination prefix itself?

1. BGP Communities
2. IP Fragmentation
3. OSPF Cost
4. MAC Learning

Correct Answer: 1

Explanation

BGP communities allow additional policy information to be associated with routes. Network operators can use communities to identify routes according to customer, geographic location, service type, routing preference, or other operational requirements. Policies can then match these communities and modify attributes or control route advertisements. Communities do not change the actual destination prefix. OSPF cost affects path selection within OSPF, MAC learning is a Layer 2 process, and IP fragmentation deals with packet size. Standard, extended, and large communities provide different ways to carry policy information across BGP environments.

Question 344

A data center requires multiple independent Layer 3 paths between leaf and spine switches. Which topology is most commonly associated with this requirement?

1. Hub-and-spoke
2. Spine-leaf
3. Ring-only
4. Single-tier

Correct Answer: 2

Explanation

The spine-leaf architecture is designed to provide predictable connectivity and multiple paths between network devices. In a typical design, every leaf connects to multiple spine switches, creating several Layer 3 paths through the fabric. ECMP can then distribute traffic across available paths. This architecture provides scalability by allowing additional leaf switches to be added for endpoints and additional spine switches to increase fabric capacity. A hub-and-spoke topology introduces a centralized dependency, while a single-tier architecture does not provide the same level of path diversity. Proper oversubscription and failure-domain planning remain important.

Question 345

Which mechanism allows a network device to detect that its next-hop neighbor is unreachable more quickly than relying only on normal routing protocol timers?

1. BFD
2. DHCP
3. DNS
4. SNMP

Correct Answer: 1

Explanation

Bidirectional Forwarding Detection (BFD) provides rapid detection of failures between neighboring network devices. Routing protocols can use relatively long hello or hold timers, while BFD can detect forwarding-path failures using much shorter intervals. Once BFD detects a failure, the associated routing protocol can react and remove or change the affected path. BFD can be integrated with protocols such as BGP, OSPF, and IS-IS depending on platform support. DHCP provides address configuration, DNS resolves names, and SNMP is primarily used for monitoring and management rather than rapid forwarding-path failure detection.

Question 346

A company wants to prioritize voice traffic and prevent large data transfers from consuming all available WAN bandwidth. Which QoS design is most appropriate?

1. Give all traffic identical treatment
2. Classify traffic and apply appropriate queuing and bandwidth policies
3. Disable congestion management
4. Increase routing protocol timers

Correct Answer: 2

Explanation

An effective QoS design first identifies important traffic classes and then applies appropriate marking, queuing, scheduling, policing, or shaping policies. Voice traffic is sensitive to delay, jitter, and packet loss, so it may require priority treatment. Large data transfers can be placed into a lower-priority class or controlled through bandwidth policies. Giving all traffic identical treatment does not address different application requirements. Routing protocol timers are unrelated to packet scheduling. QoS should be designed end-to-end, considering link speeds, traffic direction, application behavior, and provider policies.

Question 347

Which OSPF area type is designed to reduce the amount of external routing information carried inside the area while still allowing an external connection through an ASBR?

1. Stub area
2. NSSA
3. Backbone-only area
4. Transit VLAN

Correct Answer: 2

Explanation

A Not-So-Stubby Area (NSSA) allows an OSPF area to maintain restrictions on external LSAs while still permitting an ASBR inside the area to redistribute external routes. These external routes are represented using Type 7 LSAs within the NSSA and can be translated by an appropriate ABR into Type 5 LSAs for the rest of the OSPF domain. A traditional stub area does not allow an ASBR to inject normal external routes in the same way. NSSA is therefore useful when an area needs both stub-like characteristics and localized external route redistribution.

Question 348

What is a major reason for using route summarization at an OSPF ABR?

1. To reduce the number of inter-area routes
2. To disable OSPF adjacency formation
3. To increase Layer 2 broadcast traffic
4. To replace the OSPF database with BGP

Correct Answer: 1

Explanation

Route summarization at an OSPF Area Border Router can combine multiple specific prefixes into a smaller number of aggregate advertisements. This reduces the amount of inter-area routing information and can limit the impact of topology changes. It can also make routing tables easier to manage and improve overall scalability. However, summarization must be planned carefully because an aggregate may remain advertised even when some more-specific destinations are unavailable, depending on the implementation. Summarization does not disable OSPF or replace its link-state database. Proper addressing hierarchy makes effective summarization easier.

Question 349

Which technology is commonly used to provide a logical Layer 2 network over a Layer 3 IP underlay in modern data centers?

1. VXLAN
2. RIP
3. HSRP
4. NTP

Correct Answer: 1

Explanation

VXLAN creates a virtual Layer 2 overlay over a Layer 3 IP underlay. Ethernet frames are encapsulated inside UDP/IP packets and transported between VXLAN Tunnel Endpoints. This allows logical network segments to extend across a routed infrastructure without requiring the physical network to operate as one large Layer 2 domain. VXLAN is often combined with EVPN for control-plane learning and scalable endpoint advertisement. RIP is a routing protocol, HSRP provides first-hop redundancy, and NTP provides time synchronization. VXLAN designs must consider VTEP reachability, MTU, multicast or EVPN control-plane requirements, and segmentation.

Question 350

A network administrator wants to ensure that only approved prefixes are accepted from an external BGP neighbor. Which method is most appropriate?

1. Prefix filtering
2. Increasing interface MTU
3. Disabling BFD
4. Changing NTP servers

Correct Answer: 1

Explanation

Prefix filtering allows a network to explicitly define which routes are acceptable from a BGP neighbor. Prefix lists, route policies, and route maps can be used to permit approved prefixes while rejecting unexpected advertisements. This is an important security and operational control because accidental or malicious route advertisements can affect traffic forwarding and routing-table size. MTU configuration, BFD, and NTP do not provide BGP prefix control. A robust design should apply appropriate filters in both inbound and outbound directions and should account for legitimate future prefix changes without creating unnecessary operational risk.

Question 351

Which BGP attribute is normally preferred when its value is higher and is used to influence the preferred outbound exit within an autonomous system?

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

Correct Answer: 2

Explanation

Local Preference is an important BGP attribute for controlling outbound traffic within an autonomous system. Higher Local Preference values are normally preferred during BGP best-path selection. For example, an organization can assign a higher value to routes received through a preferred Internet provider and a lower value to routes received through a backup provider. MED is generally used to communicate an inbound path preference to a neighboring AS, while Origin and Router ID have different roles in BGP path selection. Local Preference is propagated through iBGP, making it useful for applying consistent outbound policies.

Question 352

Which design provides redundancy for a default gateway when two or more routers serve the same LAN segment?

1. First-hop redundancy protocol
2. DNS load balancing only
3. LDP
4. BGP communities

Correct Answer: 1

Explanation

First-hop redundancy protocols provide a virtual default gateway address that can be served by multiple routers. One device typically performs the active forwarding role while another remains available to take over when a failure occurs. Examples include HSRP, VRRP, and related mechanisms. This allows hosts to maintain a consistent default gateway address without needing to know which physical router is currently forwarding traffic. LDP is used for MPLS label distribution, BGP communities support routing policy, and DNS load balancing operates at the name-resolution level rather than directly providing first-hop gateway redundancy.

Question 353

A network designer wants to prevent a routing policy from accidentally advertising private internal prefixes to an Internet provider. What should be implemented?

1. Outbound route filtering policy
2. Larger broadcast domains
3. Disabled routing authentication
4. Unlimited route redistribution

Correct Answer: 1

Explanation

Outbound route filtering ensures that only intended prefixes are advertised to an external BGP neighbor. A carefully designed policy can explicitly permit the organization’s public prefixes and deny internal, private, or otherwise unauthorized networks. This reduces the risk of accidental route leakage and helps maintain predictable Internet routing behavior. Prefix lists, route maps, or policy frameworks can implement the required controls. Larger broadcast domains and unlimited redistribution increase operational risk, while disabling routing authentication can reduce security. External BGP sessions should generally have explicit inbound and outbound routing policies rather than relying on unrestricted advertisement.

Question 354

Which approach can improve the scalability of a large BGP deployment by reducing the number of required iBGP sessions?

1. Route reflectors
2. Static ARP
3. VLAN pruning
4. Port security

Correct Answer: 1

Explanation

Route reflectors reduce the need for a full mesh of iBGP sessions. Instead of every iBGP router establishing a session with every other router, selected route reflectors exchange routes with their clients and reflect appropriate routes between them. This greatly reduces configuration complexity as the number of BGP speakers increases. However, route-reflector placement and redundancy must be carefully designed. Poorly designed reflector topologies can affect path visibility and traffic engineering. Static ARP, VLAN pruning, and port security are unrelated to reducing iBGP session requirements.

Question 355

Which network characteristic is most important when designing a low-latency path for an interactive voice application?

1. High delay and unpredictable jitter
2. Controlled latency, jitter, and packet loss
3. Maximum routing-table size
4. Large broadcast domains

Correct Answer: 2

Explanation

Interactive voice applications are sensitive to network delay, jitter, and packet loss. A low-latency design should therefore provide predictable forwarding behavior and sufficient bandwidth while minimizing congestion. QoS mechanisms can help prioritize voice traffic during periods of contention. Network designers should also consider physical distance, link utilization, routing paths, queue behavior, and redundancy. Large broadcast domains and routing-table size do not directly provide better voice performance. The goal is not simply to maximize bandwidth but to provide predictable service characteristics that meet the application’s latency, jitter, and loss requirements.

Question 356

Which MPLS VPN component makes identical customer prefixes unique within the provider’s VPNv4 routing table?

1. Route Distinguisher
2. Route Target
3. Local Preference
4. BFD session

Correct Answer: 1

Explanation

A Route Distinguisher (RD) is used to make otherwise identical IPv4 prefixes unique within the provider’s VPNv4 routing environment. This allows different customers to use overlapping address spaces without their routes becoming indistinguishable in the provider’s BGP table. The RD provides uniqueness but does not determine which VRFs import or export the route. Route Targets perform that policy function. Local Preference influences BGP path selection, while BFD provides failure detection. Understanding the difference between RD and RT is essential when designing MPLS Layer 3 VPN services.

Question 357

Which mechanism is most suitable for controlling which VRF routes are imported into another VRF in an MPLS VPN environment?

1. Route Target
2. Route Distinguisher
3. OSPF Router ID
4. Ethernet MTU

Correct Answer: 1

Explanation

Route Targets determine the import and export policy for VPN routes between VRFs. An exported route is associated with one or more RTs, and a receiving VRF imports routes matching its configured import RTs. This mechanism enables both strict customer isolation and controlled route sharing between selected VPNs. The Route Distinguisher has a different purpose: it provides uniqueness for overlapping prefixes. OSPF Router ID identifies an OSPF router, while MTU determines the maximum packet size that can be transmitted without fragmentation. Correct RT design is therefore central to MPLS VPN segmentation.

Question 358

A network uses multiple physical links between switches and wants to treat them as one logical link for increased bandwidth and redundancy. Which technology should be used?

1. LACP
2. BGP
3. PIM
4. DHCP

Correct Answer: 1

Explanation

LACP, defined by IEEE 802.1AX, allows multiple physical Ethernet links to form a single logical Link Aggregation Group. This can provide increased aggregate bandwidth and redundancy while simplifying the logical topology presented to higher-layer protocols. Traffic is generally distributed using a hashing algorithm, so a single flow may not necessarily use every physical link simultaneously. BGP provides routing, PIM handles multicast, and DHCP provides address configuration. When designing link aggregation, engineers should consider hashing behavior, failure detection, platform limitations, cabling, and whether both sides of the connection support compatible aggregation settings.

Question 359

Which network design approach provides multiple independent physical paths while allowing routing protocols to select alternate paths after a failure?

1. Redundant routed paths
2. Single-homed connectivity
3. One shared physical cable
4. Disabled routing convergence

Correct Answer: 1

Explanation

Redundant routed paths provide alternative forwarding paths when a primary link or device fails. Dynamic routing protocols can detect topology changes and calculate alternate paths, while mechanisms such as ECMP can use multiple paths simultaneously when appropriate. Redundancy should be designed across both links and devices so that a single failure does not remove all connectivity. Single-homed connectivity and shared physical dependencies can create single points of failure. Designers should evaluate convergence time, path diversity, failure domains, bandwidth requirements, and whether redundant paths follow genuinely independent physical infrastructure.

Question 360

Which security architecture divides a network into separate trust zones and controls communication between those zones using explicit policies?

1. Network segmentation
2. Route summarization
3. ECMP
4. DNS caching

Correct Answer: 1

Explanation

Network segmentation divides infrastructure into separate security or operational zones and applies policies controlling communication between them. Segmentation can be implemented using VRFs, VLANs, firewalls, security groups, ACLs, or combinations of these technologies. The objective is to limit unnecessary communication and reduce the potential impact of a compromised system or security incident. Route summarization reduces routing information, ECMP provides multiple forwarding paths, and DNS caching improves name-resolution efficiency. A good segmentation design should consider application dependencies, east-west traffic, security inspection points, administrative boundaries, and failure behavior.