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Question 361

A network designer wants to reduce the number of routes advertised between two OSPF areas while maintaining reachability to multiple internal prefixes. Which technique should be used?

1. Route summarization
2. Increasing BFD timers
3. Disabling ECMP
4. Changing the OSPF Router ID

Correct Answer: 1

Explanation

Route summarization allows multiple specific prefixes to be represented by a single aggregate prefix. In OSPF, summarization at an ABR can reduce the number of inter-area routes and limit the amount of routing information that must be processed by routers in other areas. This can improve scalability and reduce the effect of topology changes. BFD timers, ECMP, and Router IDs do not reduce the number of advertised prefixes. Summarization should be supported by a logical addressing plan and carefully designed to avoid blackholing traffic when portions of the summarized address space become unreachable.

Question 362

Which protocol is commonly used as the interior gateway protocol in a large service-provider network because of its scalable link-state design?

1. FTP
2. IS-IS
3. DHCP
4. ARP

Correct Answer: 2

Explanation

IS-IS is widely used in large service-provider environments because it provides a scalable link-state routing architecture. It supports hierarchical Level-1 and Level-2 operation and can carry information for both IPv4 and IPv6. IS-IS also separates much of its operation from the IP addressing layer, which can be useful in provider environments. FTP is an application protocol, DHCP provides address configuration, and ARP resolves IPv4 addresses to MAC addresses. A provider choosing IS-IS should still consider area design, metric planning, convergence requirements, route summarization, and operational expertise.

Question 363

What is the primary purpose of Segment Routing in an IP/MPLS network?

1. To encode desired forwarding paths using segment information
2. To replace Ethernet switching
3. To provide automatic DNS registration
4. To eliminate IP routing completely

Correct Answer: 1

Explanation

Segment Routing allows a source or controller to influence packet forwarding by encoding a sequence of instructions, called segments, into the packet’s forwarding information. In SR-MPLS, these instructions can be represented using MPLS labels, while SRv6 uses IPv6 segment identifiers. Segment Routing can simplify traffic engineering by reducing reliance on a separate signaling protocol for every engineered path. It does not eliminate the need for routing or replace Ethernet switching. Designers should consider segment allocation, controller integration, path computation, failure handling, scalability, and interoperability when deploying Segment Routing.

Question 364

A company has two WAN providers and wants applications to dynamically select paths based on latency and packet loss. Which architecture is designed for this requirement?

1. SD-WAN
2. STP
3. LACP
4. Traditional VLAN trunking

Correct Answer: 1

Explanation

SD-WAN can dynamically evaluate multiple WAN transports and select forwarding paths based on application requirements and measured network conditions. Policies can consider characteristics such as latency, jitter, packet loss, bandwidth, and availability. This enables applications to use different links depending on their performance requirements rather than relying only on static routing metrics. STP handles Layer 2 loop prevention, LACP aggregates Ethernet links, and VLAN trunking carries multiple VLANs. A proper SD-WAN design should also address centralized policy, security, segmentation, controller availability, transport diversity, and application identification.

Question 365

Which BGP attribute is primarily intended to communicate a preferred entry point into an autonomous system to a neighboring autonomous system?

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

Correct Answer: 2

Explanation

MED, or Multi-Exit Discriminator, can be used to communicate a preference for which entry point a neighboring autonomous system should use when multiple links exist between the same autonomous systems. Lower MED values are generally preferred when the routes are being compared under applicable BGP rules. MED is therefore commonly associated with influencing inbound traffic. Local Preference is normally used internally to influence outbound traffic. Router ID identifies the BGP speaker, while Weight is a Cisco-specific attribute used locally on a router. MED should be applied with awareness of the neighboring AS’s policies and BGP comparison behavior.

Question 366

Which design choice can help prevent a Layer 2 broadcast storm from affecting the entire enterprise network?

1. Keep all users in one Layer 2 domain
2. Use Layer 3 boundaries between appropriate network segments
3. Extend every VLAN across all sites
4. Disable routing between distribution blocks

Correct Answer: 2

Explanation

Layer 3 boundaries can limit the propagation of Layer 2 broadcasts and other local-domain problems. Instead of extending one large Layer 2 domain across an entire enterprise, designers can divide the network into smaller segments and route between them. This reduces the potential impact of broadcast storms, loops, and certain Layer 2 failures. Extending every VLAN across multiple sites increases the failure domain and can create additional operational dependencies. Layer 3 boundaries also provide useful locations for security policies, routing control, and traffic filtering. The exact segmentation should reflect application and operational requirements.

Question 367

Which mechanism can be used to prevent unauthorized devices from becoming active members of an HSRP group?

1. HSRP authentication
2. Route summarization
3. ECMP
4. MPLS LDP

Correct Answer: 1

Explanation

HSRP authentication can help ensure that devices participating in an HSRP group are authorized members of the redundancy relationship. Authentication can prevent unauthorized devices from sending valid-looking HSRP messages and attempting to influence the active or standby roles. The exact authentication capabilities depend on the platform and HSRP version. Route summarization controls routing information, ECMP provides multiple forwarding paths, and LDP distributes MPLS labels. First-hop redundancy security should also be considered alongside Layer 2 protections, access controls, and management-plane security.

Question 368

A network contains multiple equal-cost paths, but traffic from a single TCP session should normally remain on one path. Which forwarding behavior supports this requirement?

1. Per-packet random forwarding
2. Per-flow hashing
3. Disabling routing
4. Broadcast forwarding

Correct Answer: 2

Explanation

Per-flow hashing distributes traffic across multiple paths while keeping packets belonging to the same flow on a consistent path. Hash inputs can include source and destination IP addresses and transport-layer port numbers. Keeping a flow on one path helps avoid packet reordering, which can negatively affect TCP performance and other applications. Per-packet load balancing can distribute individual packets independently but may introduce out-of-order delivery when paths have different characteristics. Network designers should evaluate hashing algorithms, flow distribution, path symmetry, and traffic patterns when implementing ECMP or link aggregation.

Question 369

Which protocol is commonly used to exchange routing information between autonomous systems on the Internet?

1. OSPF
2. BGP
3. STP
4. PIM

Correct Answer: 2

Explanation

Border Gateway Protocol (BGP) is the primary inter-domain routing protocol used to exchange reachability information between autonomous systems. BGP is designed around policy-based path selection and supports attributes that allow organizations to control how traffic enters and leaves their networks. OSPF is primarily an interior gateway protocol, STP prevents Layer 2 loops, and PIM handles multicast routing. BGP can also be used internally through iBGP, but its most fundamental role is exchanging routes between autonomous systems. Internet-scale BGP design requires careful filtering, policy control, redundancy, and route-security considerations.

Question 370

Which feature can provide a backup path when the primary BGP route becomes unavailable without requiring manual intervention?

1. BGP route selection and alternate-path availability
2. Static MAC learning
3. DHCP snooping
4. VLAN pruning

Correct Answer: 1

Explanation

BGP can maintain multiple eligible paths to a destination even though it normally selects one best path for forwarding. If the selected path becomes unavailable, BGP can choose another eligible route after the failure is detected and the routing process reconverges. Faster detection mechanisms such as BFD can further reduce failure-detection time. Static MAC learning, DHCP snooping, and VLAN pruning do not provide WAN routing failover. Network designers should evaluate convergence timers, route-policy consistency, alternate-path availability, and whether the backup path has sufficient bandwidth and appropriate security controls.

Question 371

Which technology is most appropriate for carrying multiple isolated customer networks across a shared MPLS provider infrastructure?

1. MPLS Layer 3 VPN
2. STP
3. HSRP
4. LACP

Correct Answer: 1

Explanation

MPLS Layer 3 VPNs allow service providers to transport multiple isolated customer networks over a shared MPLS infrastructure. Customer routes are maintained in separate VRFs, while MP-BGP can distribute VPNv4 or VPNv6 routes between provider-edge routers. Route Targets control route import and export, while Route Distinguishers provide uniqueness for overlapping prefixes. This architecture allows different customers to use identical private address ranges without necessarily causing conflicts within the provider network. STP, HSRP, and LACP solve different networking problems and do not provide the same scalable Layer 3 VPN segmentation.

Question 372

A network designer needs to transport multicast traffic between sites across an IP WAN. Which factor is especially important during the design?

1. Multicast support across the WAN transport
2. Disabling all routing protocols
3. Using only static ARP
4. Removing all redundancy

Correct Answer: 1

Explanation

Multicast WAN design requires the underlying transport to support the required multicast forwarding behavior or an appropriate mechanism to carry multicast traffic across the WAN. Designers must consider PIM operation, multicast routing boundaries, RP placement, receiver distribution, bandwidth, and provider capabilities. If native multicast is unavailable, technologies such as multicast VPN or other encapsulation mechanisms may be required depending on the environment. Disabling routing or relying on static ARP does not provide multicast distribution. Redundancy is also important because multicast applications can be sensitive to connectivity failures and convergence behavior.

Question 373

Which mechanism allows an enterprise to monitor network performance by actively testing reachability, delay, or packet loss?

1. IP SLA
2. LACP
3. VXLAN
4. STP

Correct Answer: 1

Explanation

IP SLA can generate synthetic traffic and measure network characteristics such as reachability, latency, jitter, packet loss, and response time depending on the configured operation. These measurements can help network engineers evaluate WAN quality and application-related performance. IP SLA results can also be integrated with tracking mechanisms to influence routing or failover decisions. LACP aggregates links, VXLAN provides an overlay network, and STP manages Layer 2 loop prevention. Active performance monitoring is particularly useful in WAN environments where a link may remain physically up while experiencing high latency or packet loss.

Question 374

Which design approach provides a separate routing table for different tenants on the same physical infrastructure?

1. VRF
2. NAT overload
3. STP
4. DHCP relay

Correct Answer: 1

Explanation

Virtual Routing and Forwarding (VRF) creates separate logical routing and forwarding instances on the same physical device. Each VRF can maintain its own routing table, allowing different tenants, departments, or services to use overlapping IP address spaces while maintaining traffic isolation. VRFs are widely used in enterprise segmentation, service-provider MPLS VPNs, and data-center designs. NAT overload translates addresses and ports, STP prevents Layer 2 loops, and DHCP relay forwards address-assignment requests. When deploying VRFs, designers should consider route leaking, shared services, security policies, management access, and operational complexity.

Question 375

Which method can reduce the amount of routing information exchanged between a branch network and a central enterprise network?

1. Route summarization
2. Increasing MTU
3. Enabling packet fragmentation
4. Disabling routing authentication

Correct Answer: 1

Explanation

Route summarization aggregates multiple prefixes into a larger address block, reducing the number of individual routes exchanged between network domains. In branch environments, this can simplify routing tables and reduce the impact of route changes. Effective summarization depends on an appropriate addressing hierarchy. Increasing MTU changes packet-size capability but does not reduce routing information. Fragmentation can actually introduce additional processing overhead, and disabling authentication does not improve routing scalability. Designers should verify that summarized prefixes accurately represent reachable networks and that failures inside the summarized range do not cause undesirable traffic blackholing.

Question 376

Which component in an EVPN-VXLAN fabric commonly distributes MAC and IP reachability information between VTEPs?

1. MP-BGP EVPN control plane
2. DHCP server
3. NTP server
4. LACP partner

Correct Answer: 1

Explanation

MP-BGP EVPN provides the control plane used to exchange endpoint reachability information in many EVPN-VXLAN deployments. VTEPs advertise information such as MAC addresses, IP addresses, Ethernet segments, and associated VNIs using EVPN routes. This reduces dependence on traditional flood-and-learn behavior and provides a scalable mechanism for distributing endpoint information. DHCP assigns IP addresses, NTP synchronizes time, and LACP manages link aggregation. A robust EVPN-VXLAN design should also consider route-reflector placement, VTEP redundancy, multihoming, underlay reachability, MTU, and control-plane scalability.

Question 377

Which routing design is most appropriate when an organization wants to use one preferred Internet connection while retaining another connection as a backup?

1. Apply higher Local Preference to routes learned from the preferred connection
2. Apply higher Local Preference to the backup connection
3. Remove all BGP routes
4. Disable the IGP

Correct Answer: 1

Explanation

Higher Local Preference normally makes routes more attractive for outbound traffic within an autonomous system. By assigning a higher Local Preference to routes learned through the preferred Internet connection, internal routers will generally select that path while the second connection remains available as an alternative. If the primary path becomes unavailable, BGP can select an eligible backup route. The policy should be applied consistently across relevant internal routers. The design should also consider inbound traffic separately because Local Preference primarily controls outbound path selection, while techniques such as AS-path prepending or MED may influence inbound decisions.

Question 378

What is the primary benefit of using route filtering at network boundaries?

1. It controls which routing information is accepted or advertised
2. It increases Ethernet frame size
3. It replaces all security controls
4. It disables routing convergence

Correct Answer: 1

Explanation

Route filtering provides control over which prefixes are accepted from or advertised to neighboring routing domains. This can prevent accidental route leaks, limit unnecessary routing information, enforce business policies, and protect routing-table resources. Filtering can be implemented using prefix lists, route maps, policy statements, communities, or other routing-policy mechanisms depending on the platform. Route filtering is not a replacement for firewall or other security controls, and it does not directly affect Ethernet frame size. A well-designed policy should explicitly define expected prefixes and include safeguards against unintended changes.

Question 379

A company wants to automate configuration and collect operational information from thousands of network devices. Which approach best supports this requirement?

1. Network automation and centralized telemetry
2. Manual CLI configuration only
3. Static ARP on every device
4. Physical console access for every change

Correct Answer: 1

Explanation

Network automation can standardize configuration deployment, reduce repetitive manual work, and improve consistency across large device populations. Centralized telemetry can provide continuous operational information that automation or monitoring systems can use for visibility and analysis. Modern automation may use APIs, model-driven interfaces, configuration templates, orchestration systems, and streaming telemetry. Manual CLI and physical console access do not scale efficiently to thousands of devices and can increase configuration inconsistency. A scalable automation architecture should also address authentication, authorization, version control, change validation, rollback, observability, and failure handling.

Question 380

Which design principle is most important when building a highly available network service?

1. Eliminate every redundant component
2. Remove single points of failure
3. Use one centralized physical link
4. Depend on manual recovery for every failure

Correct Answer: 2

Explanation

High availability requires identifying and eliminating or mitigating single points of failure. This can involve redundant devices, diverse physical links, multiple power sources, clustered services, state synchronization, dynamic routing, and automated failover. Redundancy should be designed across the complete service path rather than focusing on only one component. A network with two redundant routers connected through the same physical cable, for example, may still have a common failure point. Designers should evaluate failure scenarios, convergence time, state preservation, operational complexity, and the actual availability requirements of the business service.