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Question 381

A network designer needs to provide IPv6 connectivity while the existing WAN infrastructure is still primarily IPv4. Which transition technique can carry IPv6 traffic across an IPv4-only transport network?

1. IPv6 tunneling over IPv4
2. BGP Local Preference
3. MPLS Route Target
4. LACP

Correct Answer: 1

Explanation

IPv6 tunneling over an IPv4 transport allows IPv6 packets to be encapsulated inside IPv4 packets so they can traverse infrastructure that does not yet provide native IPv6 forwarding. This can be useful during a gradual migration when replacing or upgrading the entire WAN is not immediately practical. The exact tunneling method depends on the network architecture and operational requirements. Local Preference controls BGP path selection, Route Targets control MPLS VPN route import and export, and LACP aggregates Ethernet links. Tunnel overhead, MTU, security, routing, and failure handling should be considered during design.

Question 382

Which BGP mechanism allows a router to advertise the same route information to multiple iBGP clients without requiring a full-mesh iBGP topology?

1. Route reflector
2. PIM RP
3. DHCP relay
4. HSRP

Correct Answer: 1

Explanation

A BGP route reflector reduces the requirement for a full mesh of iBGP sessions. Client routers establish iBGP sessions with the route reflector, which can reflect appropriate routes between its clients and other BGP peers. This significantly improves scalability as the number of iBGP routers grows. Route-reflector clusters can also be designed with redundant reflectors to avoid creating a single point of failure. PIM Rendezvous Points support multicast, DHCP relay forwards address-assignment requests, and HSRP provides first-hop redundancy. Route-reflector design should consider path visibility, redundancy, policy, and topology.

Question 383

Which QoS mechanism limits traffic to a specified rate and can discard or remark packets that exceed the configured rate?

1. Policing
2. Route summarization
3. ECMP
4. BGP reflection

Correct Answer: 1

Explanation

QoS policing monitors traffic against a configured rate and takes an action when traffic exceeds the allowed rate. Depending on the policy, excess packets may be dropped or remarked. Policing is commonly used at network boundaries where traffic must conform to a service or bandwidth agreement. Traffic shaping is different because shaping generally buffers excess traffic and transmits it later at a controlled rate. Route summarization, ECMP, and BGP route reflection address routing and forwarding scalability rather than bandwidth enforcement. Designers should select policing or shaping according to application requirements and where congestion occurs.

Question 384

Which OSPF LSA type is used to advertise external routes redistributed into a normal OSPF area?

1. Type 3
2. Type 5
3. Type 1
4. Type 2

Correct Answer: 2

Explanation

Type 5 LSAs are used to advertise external routes that have been redistributed into an OSPF autonomous system by an Autonomous System Boundary Router (ASBR). These routes can originate from another routing protocol, static routing, or another external source. Type 1 LSAs describe router information, Type 2 LSAs are associated with multiaccess network information from a DR, and Type 3 LSAs carry inter-area network information. NSSA areas use Type 7 LSAs for external routes within the NSSA, which can be translated to Type 5 by an appropriate ABR.

Question 385

A company wants to ensure that traffic between two critical data centers continues even if one physical WAN circuit fails. Which design should be considered?

1. Diverse redundant WAN connectivity
2. Single WAN circuit
3. One shared physical path
4. Manual route changes only

Correct Answer: 1

Explanation

Diverse redundant WAN connectivity provides alternate paths between critical locations. For meaningful resilience, the redundant circuits should ideally use physically and logically diverse infrastructure rather than simply purchasing two services that share the same underlying cable or provider path. Dynamic routing, SD-WAN policies, or other failover mechanisms can automatically select the surviving path. A single circuit creates a direct single point of failure, while manual route changes increase recovery time. Designers should evaluate provider diversity, physical path diversity, bandwidth, latency, convergence, security, and whether the backup circuit can support critical workloads.

Question 386

Which technology allows an enterprise to carry multiple VLANs over a single physical Ethernet connection between switches?

1. 802.1Q trunking
2. BFD
3. BGP
4. NAT64

Correct Answer: 1

Explanation

IEEE 802.1Q trunking allows multiple VLANs to traverse the same physical Ethernet connection by adding VLAN identification information to Ethernet frames. This is commonly used between switches, routers, firewalls, and other network devices that need connectivity to multiple VLANs. Trunk design should consider allowed VLAN lists, native VLAN behavior, security, MTU, and redundancy. BFD provides rapid failure detection, BGP exchanges routing information, and NAT64 facilitates communication between IPv6 and IPv4 environments. Although trunking is useful, large-scale designs should avoid unnecessary Layer 2 extension across failure domains.

Question 387

Which technology is designed to provide Layer 2 multipathing and loop prevention in modern data-center networks without relying solely on traditional STP?

1. EVPN
2. FTP
3. NTP
4. DHCP

Correct Answer: 1

Explanation

EVPN provides a control-plane framework for exchanging Ethernet reachability information and can support scalable Layer 2 services over routed infrastructure. When combined with VXLAN, EVPN enables modern data-center fabrics with distributed gateways, endpoint learning, multihoming, and controlled Layer 2 extension. This architecture reduces dependence on traditional spanning-tree-based designs for many data-center use cases. FTP is an application protocol, NTP synchronizes time, and DHCP provides address configuration. EVPN designs should consider route types, VTEP connectivity, multihoming, failure convergence, route-reflector architecture, and underlay scalability.

Question 388

Which BGP attribute is generally preferred when its value is lower and can be used to influence inbound traffic toward a network?

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

Correct Answer: 1

Explanation

MED, or Multi-Exit Discriminator, is commonly used to communicate a preference to a neighboring autonomous system when multiple connections exist between the same organizations. Lower MED values are generally preferred when the relevant BGP comparison rules apply. This can influence which entry point another AS selects for reaching the advertising network. Local Preference is normally used internally to influence outbound traffic, while Weight is a local Cisco-specific attribute. Router ID identifies a BGP speaker. MED should not be treated as a guaranteed inbound traffic-control mechanism because remote routing policies and other BGP attributes can override its influence.

Question 389

Which network service translates a hostname such as server.example.com into an IP address?

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

Correct Answer: 1

Explanation

The Domain Name System (DNS) translates human-readable domain or host names into IP addresses and can also provide other types of service records. DNS is a fundamental dependency for many applications and should be designed with appropriate redundancy, caching, security, and monitoring. DHCP is primarily responsible for dynamically providing IP configuration information to hosts. BFD detects forwarding-path failures, while LACP manages link aggregation. Enterprise DNS architecture may include internal authoritative servers, recursive resolvers, caching, split-horizon DNS, and secure DNS practices depending on the organization’s requirements.

Question 390

A network designer wants to prevent one tenant from accessing another tenant’s traffic while sharing the same physical switches. Which feature is most appropriate?

1. VRF-based segmentation
2. Shared global routing table only
3. Unrestricted route redistribution
4. Single Layer 2 broadcast domain

Correct Answer: 1

Explanation

VRF-based segmentation creates separate logical routing tables on shared physical infrastructure. Each tenant can maintain independent routing information, which helps prevent unintended traffic exchange between tenants. Additional security policies such as ACLs or firewalls may be required when controlled communication between tenants is needed. A single global routing table provides less isolation, while unrestricted route redistribution can accidentally expose routes between tenants. A single large Layer 2 broadcast domain can also increase the failure and security domain. VRF design should include clear route-leaking policies for approved shared services.

Question 391

Which mechanism can be used to control route redistribution between two different routing protocols?

1. Route policy
2. Ethernet MTU
3. LACP
4. NTP

Correct Answer: 1

Explanation

Route policies can control which prefixes are redistributed between different routing protocols and can modify attributes during redistribution. This is important because unrestricted redistribution can create routing loops, excessive route advertisements, or unexpected path selection. Designers can use prefix lists, route maps, policy statements, tags, metrics, or other mechanisms to carefully control redistribution. MTU affects packet transmission size, LACP manages link aggregation, and NTP synchronizes device clocks. Whenever redistribution is required, engineers should define route ownership, filtering, metric behavior, loop prevention, and failure scenarios before implementing the policy.

Question 392

Which design approach can reduce routing-table size when a group of contiguous prefixes can be represented by one larger prefix?

1. Route aggregation
2. Packet fragmentation
3. MAC flooding
4. VLAN translation

Correct Answer: 1

Explanation

Route aggregation, also called summarization, represents multiple more-specific prefixes with a single aggregate prefix. This reduces routing-table size and can decrease the amount of routing information exchanged between network domains. Aggregation is especially useful in hierarchical enterprise and service-provider designs where address allocation follows logical boundaries. However, designers must ensure that the aggregate does not incorrectly attract traffic toward unavailable destinations. Packet fragmentation, MAC flooding, and VLAN translation do not reduce Layer 3 routing information. Address planning is therefore an important prerequisite for effective and predictable route aggregation.

Question 393

Which component in an SD-WAN architecture is typically responsible for centralized policy and orchestration?

1. SD-WAN controller or management plane
2. Ethernet access switch only
3. DHCP client
4. DNS cache

Correct Answer: 1

Explanation

SD-WAN architectures commonly use centralized management and control components to define policies, distribute configuration, monitor network conditions, and coordinate edge devices. The exact roles and terminology vary between vendors, but the architecture generally separates centralized control and management functions from packet forwarding performed by edge devices. This allows policies to be applied consistently across many sites. An Ethernet access switch, DHCP client, or DNS cache does not provide the centralized orchestration role. Designers should evaluate controller redundancy, secure communication, scalability, policy distribution, and how the system behaves if control-plane connectivity is temporarily unavailable.

Question 394

Which technology can provide rapid detection of a failure on a routed link and notify a routing protocol to reconverge?

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

Correct Answer: 1

Explanation

BFD is specifically designed for rapid detection of forwarding-path failures. It can operate independently of a routing protocol while providing failure information to protocols such as OSPF, IS-IS, or BGP when supported. This allows routing convergence to begin sooner than would be possible using only standard protocol timers. BFD does not assign addresses or resolve names. STP is designed for Layer 2 loop prevention. BFD deployment should consider session scale, timer values, CPU utilization, hardware support, and whether rapid failure detection is actually required for every link.

Question 395

Which approach is most appropriate for providing Internet access from branch offices while allowing local traffic to exit directly rather than returning to a central data center?

1. Local Internet breakout
2. Centralized hairpinning only
3. Disabling branch routing
4. Removing security policies

Correct Answer: 1

Explanation

Local Internet breakout allows branch traffic destined for Internet services to exit directly through a local Internet connection rather than being backhauled through a central data center. This can reduce latency, conserve WAN bandwidth, and improve application performance for cloud-based services. However, the design must include appropriate security controls such as firewalls, secure DNS, web filtering, or SD-WAN security policies depending on organizational requirements. Centralized hairpinning may increase latency and WAN utilization. Local breakout should therefore be evaluated alongside security, compliance, resiliency, and operational-management requirements.

Question 396

Which factor should be considered when designing a network for applications that are highly sensitive to packet loss?

1. Congestion and QoS behavior
2. Only the number of VLANs
3. DNS record length
4. MAC address format

Correct Answer: 1

Explanation

Applications that are sensitive to packet loss require careful consideration of congestion, queue behavior, available bandwidth, link quality, and QoS policies. Packet loss can result from overloaded links, insufficient buffers, physical errors, provider policing, or network failures. QoS can prioritize critical traffic and help control congestion, but it cannot create bandwidth that does not exist. Designers should also consider redundancy, monitoring, application behavior, and end-to-end performance. VLAN count, DNS record length, and MAC address format do not directly determine whether a network can meet an application’s packet-loss requirements.

Question 397

Which routing technique can be used to direct selected traffic through a different next hop instead of relying solely on the destination-based routing table?

1. Policy-Based Routing
2. Route summarization
3. LACP
4. NTP

Correct Answer: 1

Explanation

Policy-Based Routing (PBR) allows traffic to be forwarded according to defined policies rather than only the normal destination-based routing decision. Policies can match characteristics such as source address, destination address, protocol, or other supported fields and then specify an alternate next hop or forwarding action. PBR can be useful for service insertion, traffic engineering, or application-specific forwarding. However, excessive use can make troubleshooting and network behavior more complex. Route summarization, LACP, and NTP do not provide policy-based packet forwarding. PBR should therefore be applied selectively and documented carefully.

Question 398

Which design principle helps ensure that a network can continue operating when a single physical link or device fails?

1. Redundancy and path diversity
2. Single-homed connectivity
3. One shared power source
4. Manual-only failover

Correct Answer: 1

Explanation

Redundancy and path diversity provide alternative resources when a network component fails. Effective redundancy should include not only multiple devices and links but also diverse physical paths, power sources, providers, and failure domains where appropriate. Dynamic routing, first-hop redundancy, link aggregation, and stateful failover can automate recovery depending on the network layer and service. Simply adding two connections that share the same physical conduit may not provide true resilience. Designers should identify realistic failure scenarios and verify that the remaining infrastructure has enough capacity to maintain critical services during the failure.

Question 399

Which IPv6 address type is automatically configured on an IPv6-enabled interface and is used for communication on the local link?

1. Link-local address
2. Global unicast address
3. Multicast-only address
4. Anycast-only address

Correct Answer: 1

Explanation

IPv6 interfaces automatically generate a link-local address when IPv6 is enabled. Link-local addresses are used for communication within the local Layer 2 segment and are essential for many IPv6 neighbor and routing functions. They are not globally routable and remain limited to the local link. Global unicast addresses are used for broader routed connectivity, while multicast addresses represent groups of receivers. Anycast uses an address assigned to multiple interfaces and is not a separate basic address-generation mechanism in the same sense. IPv6 designs should account for link-local addressing even when global addressing is also configured.

Question 400

A network designer wants to improve operational visibility by collecting interface counters, routing information, and device health data continuously. Which technology is best suited to this requirement?

1. Streaming telemetry
2. Static routing
3. NAT
4. STP

Correct Answer: 1

Explanation

Streaming telemetry provides continuous or near-real-time operational data from network devices to monitoring and analytics systems. It can expose information such as interface counters, CPU and memory utilization, routing state, queue statistics, environmental data, and other operational metrics. Compared with traditional periodic polling, streaming telemetry can provide more timely visibility and support automation and proactive troubleshooting. Static routing, NAT, and STP perform forwarding or network-control functions rather than continuous operational data collection. A scalable telemetry architecture should consider data models, collection frequency, transport security, storage, alerting, and the volume of generated data.