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Question 321

A network designer wants OSPF routers in a large enterprise to minimize the amount of topology information exchanged between different parts of the network. Which approach is most appropriate?

1. Use OSPF areas with a hierarchical design
2. Disable OSPF adjacency formation
3. Place all routers in separate autonomous systems
4. Redistribute every route into RIP

Correct Answer: 1

Explanation

OSPF areas provide a hierarchical structure that can improve scalability in large networks. Routers within an area maintain detailed topology information for that area, while ABRs exchange summarized inter-area information. This reduces the amount of topology information that every router must maintain and can also limit the scope of SPF calculations. Placing every router in a separate autonomous system would create unnecessary complexity, while RIP is not an appropriate solution for a large enterprise. A carefully designed OSPF hierarchy should also consider Area 0 placement, summarization, redundancy, and failure domains.

Question 322

Which OSPF LSA type is primarily used by an ABR to advertise networks from one OSPF area into another area?

1. Type 5
2. Type 7
3. Type 3
4. Type 1

Correct Answer: 3

Explanation

Type 3 LSAs, also called Summary LSAs, are generated by OSPF Area Border Routers to advertise inter-area network information. They allow routers in one OSPF area to learn about prefixes located in another area without requiring the complete internal topology of that remote area. Type 1 LSAs describe router information within an area, while Type 5 LSAs carry external routes redistributed into OSPF. Type 7 LSAs are associated with external routes in NSSA areas. Understanding LSA types is important when designing OSPF area boundaries, summarization, route filtering, and external connectivity.

Question 323

A company has two Internet links and wants internal BGP routers to prefer one link for outbound traffic. Which BGP attribute should be manipulated?

1. MED
2. Local Preference
3. AS Path
4. Origin

Correct Answer: 2

Explanation

Local Preference is the standard BGP attribute used inside an autonomous system to influence outbound traffic. A higher Local Preference is normally preferred, allowing an organization to designate one Internet connection as the primary exit while keeping another available as a backup. The value can be applied to routes received from different providers and propagated through iBGP. AS-path prepending is more commonly used to influence inbound traffic, while MED can also influence path selection by a neighboring AS under appropriate conditions. Origin is a lower-level BGP path-selection attribute and is not normally the primary tool for this requirement.

Question 324

Which design approach can help reduce the impact of a single network failure across a large enterprise?

1. Increase the size of every broadcast domain
2. Create appropriate failure domains
3. Remove all redundant links
4. Use one centralized router for all traffic

Correct Answer: 2

Explanation

Failure-domain design limits the portion of the network affected when a device, link, or service fails. Appropriate segmentation can prevent a local failure from propagating across the entire infrastructure. Examples include separating Layer 2 domains, using routing boundaries, deploying redundant distribution blocks, and controlling failure propagation between data centers. Increasing broadcast domains can increase the potential impact of Layer 2 problems, while removing redundancy creates additional single points of failure. A centralized router may also become a critical dependency. Good architecture balances fault isolation, operational simplicity, redundancy, and acceptable convergence behavior.

Question 325

In an IS-IS network, which design characteristic generally improves scalability?

1. Using a hierarchical Level-1/Level-2 architecture
2. Disabling all route summarization
3. Placing every router in Level 1 only
4. Replacing IS-IS with ARP

Correct Answer: 1

Explanation

IS-IS supports a hierarchical architecture using Level-1 and Level-2 routing. Level-1 routers primarily handle routing within an area, while Level-2 routers provide connectivity between areas. This hierarchy can reduce the amount of detailed topology information required throughout a large network and provides a structure for scaling the routing domain. Route summarization and careful area design can further improve scalability. Using only Level-1 routers would not provide the same hierarchical inter-area structure. ARP is a local address-resolution protocol and has no role in replacing an interior routing protocol such as IS-IS.

Question 326

What is a primary advantage of using BGP communities in an enterprise or service-provider network?

1. They provide a mechanism to tag routes for policy decisions
2. They automatically encrypt BGP sessions
3. They replace IP addressing
4. They prevent all routing loops

Correct Answer: 1

Explanation

BGP communities allow routes to be tagged with policy information that can be interpreted by routers and routing policies. An organization can use communities to identify routes according to business requirements, customer type, geographic region, service class, or desired routing treatment. Policies can then modify attributes or control route advertisements based on those tags. Communities do not encrypt BGP sessions; TCP authentication and security mechanisms are used for that purpose. They also do not replace addressing or inherently prevent every routing loop. Standard and extended communities provide flexible policy signaling across complex BGP environments.

Question 327

A network uses two equal-cost paths between routers. Which forwarding mechanism can distribute traffic across both paths?

1. ECMP
2. STP BPDU filtering
3. NAT64
4. DHCP snooping

Correct Answer: 1

Explanation

Equal-Cost Multipath (ECMP) allows a router to install and use multiple paths with equal routing cost toward the same destination. Traffic can then be distributed across those paths using a forwarding hash, commonly based on fields such as source and destination IP addresses and transport ports. ECMP can improve bandwidth utilization and provide redundancy. The exact load-sharing behavior depends on platform and hashing configuration. STP BPDU filtering, NAT64, and DHCP snooping serve different purposes and do not provide Layer 3 equal-cost forwarding. Designers should also consider asymmetric paths, flow polarization, and application traffic patterns.

Question 328

Which mechanism is commonly used to prevent a BGP speaker from accepting routes containing its own AS number?

1. Split horizon
2. AS-path loop detection
3. Spanning Tree Protocol
4. MAC filtering

Correct Answer: 2

Explanation

BGP uses the AS_PATH attribute to detect routing loops. When a BGP speaker receives a route advertisement containing its own autonomous system number in the AS_PATH, it normally rejects the route because accepting it could create a routing loop. This mechanism is fundamental to inter-domain BGP operation. Split horizon is associated with other routing technologies, while STP operates at Layer 2 and MAC filtering controls Ethernet forwarding behavior. Network designers should also understand how route reflectors, confederations, and route policies interact with BGP loop-prevention mechanisms in larger deployments.

Question 329

Which IPv6 feature allows multiple addresses to be assigned to the same interface for different purposes?

1. IPv6 multicast only
2. IPv6 addressing with multiple unicast addresses
3. DHCPv4 relay
4. MPLS label stacking

Correct Answer: 2

Explanation

IPv6 interfaces can have multiple addresses simultaneously, including link-local, global unicast, unique local, and potentially other address types depending on the design. This capability supports functions such as local-link communication, global reachability, and service-specific addressing. Link-local addresses are essential for many IPv6 control-plane operations, while global addresses provide routable connectivity. DHCPv4 relay applies to IPv4 address assignment, and MPLS label stacking is unrelated to IPv6 addressing. IPv6 network design should carefully consider addressing plans, prefix allocation, routing boundaries, security policies, and whether hosts use SLAAC, DHCPv6, or both.

Question 330

A network designer wants to ensure that a critical application receives preferential treatment during periods of congestion. Which QoS function is most directly responsible for placing traffic into an appropriate queue?

1. Classification
2. Queuing
3. DNS resolution
4. Route summarization

Correct Answer: 2

Explanation

Queuing determines how packets are stored and scheduled when an interface becomes congested. After traffic has been classified and often marked, QoS mechanisms can place different traffic classes into appropriate queues and assign scheduling behavior. Critical applications such as voice may receive a dedicated or prioritized queue depending on the design. Classification identifies the traffic, while marking communicates its treatment requirements. Route summarization and DNS resolution have no role in congestion queue scheduling. Effective QoS design should consider application requirements, bandwidth availability, packet size, latency, jitter, loss sensitivity, and traffic direction.

Question 331

Which technology is designed to provide rapid state synchronization between redundant network devices?

1. Stateful redundancy mechanisms
2. DNS caching
3. Route summarization
4. VLAN pruning

Correct Answer: 1

Explanation

Stateful redundancy mechanisms synchronize relevant operational information between active and standby devices. Depending on the platform, this can include connection state, forwarding information, or other control-plane and data-plane information. The goal is to allow a standby device to assume forwarding responsibility with minimal disruption when the active device fails. DNS caching improves name-resolution performance, route summarization reduces routing information, and VLAN pruning limits unnecessary VLAN traffic. Stateful redundancy is especially valuable for services where rebuilding connection state after a failure would cause significant disruption.

Question 332

A data center has multiple Layer 3 paths between switches. Which design provides fast convergence without depending on a large Layer 2 spanning-tree domain?

1. Routed underlay with ECMP
2. Single Layer 2 VLAN across all switches
3. One physical uplink per switch
4. Disabling IP routing

Correct Answer: 1

Explanation

A routed underlay using ECMP provides multiple Layer 3 paths and allows traffic to use available equal-cost routes. This design avoids extending large Layer 2 broadcast domains across the entire data center and reduces dependence on Spanning Tree Protocol for path selection. Layer 3 routing can also provide faster and more predictable convergence when a link or device fails. A single Layer 2 VLAN can increase the failure domain, while using only one physical uplink removes path redundancy. Modern data-center architectures commonly use routed underlays as the foundation for overlays such as VXLAN.

Question 333

What is the primary purpose of a route reflector in an iBGP network?

1. To reduce the requirement for a full mesh of iBGP sessions
2. To replace the IGP
3. To encrypt all BGP updates
4. To eliminate the AS_PATH attribute

Correct Answer: 1

Explanation

Traditional iBGP requires a full mesh of sessions between participating routers to ensure routes are properly propagated. As the number of routers grows, the number of sessions becomes difficult to manage. A route reflector provides a scalable alternative by allowing selected routers to reflect BGP routes between clients. This significantly reduces the number of required iBGP sessions. Route reflectors do not replace the underlying IGP, encrypt BGP updates, or eliminate AS_PATH. Designers should consider reflector placement, redundancy, cluster design, path visibility, and potential routing-policy implications when deploying route reflectors.

Question 334

Which approach is commonly used to influence inbound traffic toward a specific Internet connection by making another path appear less attractive?

1. Increasing Local Preference
2. AS-path prepending
3. Increasing OSPF cost internally
4. Changing DHCP lease duration

Correct Answer: 2

Explanation

AS-path prepending adds additional instances of an autonomous system number to the AS_PATH of advertised routes. Because BGP generally prefers shorter AS paths when comparing otherwise eligible paths, prepending can make a route appear less attractive to external networks. This technique is commonly used to influence inbound traffic, although the actual result depends on the remote network’s policies and other BGP attributes. Local Preference is normally used for outbound traffic within an autonomous system. OSPF cost affects internal routing and DHCP lease duration has no meaningful effect on BGP path selection.

Question 335

A network uses PIM Sparse Mode. What is the primary role of the Rendezvous Point in the initial multicast distribution process?

1. It provides a meeting point for sources and receivers using the shared tree
2. It assigns IP addresses to multicast receivers
3. It encrypts multicast packets
4. It replaces the unicast routing table

Correct Answer: 1

Explanation

In PIM Sparse Mode, the Rendezvous Point (RP) acts as a central point for initial multicast distribution using a shared tree. Multicast sources can register information with the RP, while receivers can join the shared tree toward the RP. Depending on the design and traffic conditions, routers may later establish a shortest-path tree directly toward the source. RP placement and redundancy are important because the RP plays a significant role in initial multicast operation. The RP does not assign host addresses, encrypt multicast traffic, or replace the underlying unicast routing system.

Question 336

Which network design principle helps prevent a failure in one data center from unnecessarily affecting services in another data center?

1. Failure-domain isolation
2. Extending every VLAN between sites
3. Using one shared gateway for all sites
4. Removing routing boundaries

Correct Answer: 1

Explanation

Failure-domain isolation limits the propagation of failures between independent parts of the network. In multi-data-center environments, designers can use routing boundaries, controlled Layer 2 extension, redundant services, and independent infrastructure to prevent a local problem from affecting remote sites unnecessarily. Extending every VLAN between data centers can increase the blast radius of Layer 2 problems and create operational complexity. Similarly, using one shared gateway or removing routing boundaries can create excessive dependencies. The appropriate design depends on application requirements, disaster-recovery objectives, latency, and the amount of state that must remain synchronized.

Question 337

Which WAN architecture allows different branches to establish direct connectivity for selected applications while maintaining centralized policy control?

1. SD-WAN
2. STP
3. LACP
4. HSRP only

Correct Answer: 1

Explanation

SD-WAN architectures can provide centralized policy and orchestration while dynamically selecting paths between sites based on application requirements and link conditions. Depending on the implementation, traffic can use direct site-to-site paths rather than always traversing a central hub. Policies can consider latency, packet loss, jitter, bandwidth, security, and application identity. STP and LACP address Layer 2 functions, while HSRP provides first-hop gateway redundancy. SD-WAN therefore provides a framework for combining multiple WAN transports with centralized policy, dynamic path selection, segmentation, and operational automation.

Question 338

A company needs to inspect traffic between security zones without forcing all traffic through a single centralized firewall. Which architecture can help accomplish this?

1. Distributed firewall or service insertion
2. Single unmanaged switch
3. Static ARP entries
4. DHCP relay

Correct Answer: 1

Explanation

Distributed firewall architectures and service-insertion designs can place security enforcement closer to the traffic source or between defined network segments. This can reduce unnecessary traffic tromboning through a centralized security device and can improve scalability in large data-center or cloud environments. The exact architecture may involve physical firewalls, virtual appliances, service chains, or distributed security functions. Static ARP and DHCP relay do not provide traffic inspection. A network designer should consider throughput, state synchronization, failure behavior, routing symmetry, segmentation requirements, and operational management when distributing security services.

Question 339

Which protocol is commonly used to synchronize clocks across network devices and servers?

1. NTP
2. BGP
3. VXLAN
4. LACP

Correct Answer: 1

Explanation

Network Time Protocol (NTP) is commonly used to synchronize clocks across routers, switches, servers, and other devices. Accurate time is important for troubleshooting, event correlation, authentication systems, logging, monitoring, and security investigations. In larger environments, organizations may deploy redundant internal NTP sources synchronized to reliable external references. BGP handles inter-domain routing, VXLAN provides network virtualization, and LACP provides link aggregation. NTP design should consider source reliability, authentication where required, hierarchy, redundancy, and protection against unauthorized time sources.

Question 340

A network designer needs to provide IPv4 Internet access to users while conserving globally routable IPv4 addresses. Which technology is commonly used?

1. NAT/PAT
2. OSPF
3. EVPN
4. LDP

Correct Answer: 1

Explanation

Network Address Translation (NAT), particularly Port Address Translation (PAT), allows multiple private IPv4 hosts to share one or a small number of public IPv4 addresses. PAT differentiates simultaneous sessions using transport-layer port information. This helps conserve limited public IPv4 address space and is widely deployed at enterprise Internet edges. OSPF is an interior routing protocol, EVPN provides VPN and Ethernet virtualization capabilities, and LDP distributes MPLS labels. NAT introduces considerations such as session state, application compatibility, logging, troubleshooting, and high-availability design, so it should be incorporated carefully into the overall network architecture.