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Question 281

A network architect is designing a large enterprise campus and wants to minimize the size of Layer 2 domains while providing fast inter-subnet connectivity. Which approach is most appropriate?

1. Extend one VLAN across the entire campus
2. Use Layer 3 routing between access blocks
3. Create one large spanning-tree domain
4. Use transparent bridging between all buildings

Correct Answer: 2

Explanation

Using Layer 3 routing between access blocks limits the size of Layer 2 domains and reduces the potential impact of Layer 2 failures. Each access block can maintain its own VLANs while Layer 3 switches provide routed connectivity between different parts of the campus. This design can improve scalability, simplify troubleshooting, and reduce dependence on spanning-tree convergence across large areas. Extending a single VLAN or spanning-tree domain throughout the campus increases the failure and broadcast domains. Therefore, Layer 3 routing between access blocks is the appropriate scalable design approach.

Question 282

An organization needs to allow only selected prefixes from an external BGP neighbor into its routing table. Which mechanism provides the required control?

1. Prefix list
2. HSRP
3. LACP
4. STP

Correct Answer: 1

Explanation

A prefix list can explicitly define which IP prefixes are permitted or denied when applying a routing policy. When attached to an inbound BGP policy, it allows an administrator to accept only authorized prefixes from an external neighbor. This protects the routing table from unexpected advertisements and can also help prevent route leaks or excessive route growth. HSRP provides gateway redundancy, LACP aggregates physical links, and STP prevents Layer 2 loops. A prefix list is therefore the appropriate mechanism for controlling which BGP prefixes are accepted.

Question 283

A data center requires a scalable overlay that supports many isolated Layer 2 segments over a common Layer 3 infrastructure. Which technology provides the overlay encapsulation?

1. VXLAN
2. OSPF
3. BFD
4. HSRP

Correct Answer: 1

Explanation

VXLAN provides an overlay mechanism that encapsulates Layer 2 Ethernet frames inside UDP/IP packets so that logical Layer 2 networks can operate across a Layer 3 underlay. VXLAN uses a 24-bit VNI, allowing significantly more logical segments than traditional 12-bit VLAN identifiers. This makes it suitable for large multi-tenant data center environments. OSPF provides routing, BFD provides rapid failure detection, and HSRP provides first-hop redundancy. VXLAN is therefore the technology responsible for providing scalable Layer 2 overlay segmentation across a routed infrastructure.

Question 284

A company wants to influence inbound traffic from an external autonomous system by making one advertised route less preferred without changing the destination prefix. Which technique can be used?

1. AS-path prepending
2. Local Preference
3. HSRP
4. Route summarization

Correct Answer: 1

Explanation

AS-path prepending adds additional copies of the local AS number to the AS-path of an advertised BGP route. This can make the path appear longer to external autonomous systems and therefore potentially less attractive when other path-selection attributes are equivalent. It is commonly used as an inbound traffic-engineering mechanism. Local Preference primarily affects outbound path selection within the local AS. HSRP provides gateway redundancy, while route summarization reduces routing information. AS-path prepending is therefore appropriate when the objective is to influence how external networks select an inbound path.

Question 285

A network architect needs multiple routers to advertise the same service address so that clients can reach a nearby service instance. Which addressing model should be considered?

1. Anycast
2. Broadcast
3. Multicast
4. Private VLAN

Correct Answer: 1

Explanation

Anycast allows multiple geographically or topologically distributed devices to advertise the same IP address. Routing then determines which instance is reached, typically directing clients toward an appropriate or topologically closer service location. This approach is widely useful for distributed services such as DNS and other globally distributed applications. Broadcast sends traffic to all devices within a broadcast domain, while multicast delivers traffic to subscribed receivers. Private VLANs provide Layer 2 isolation and are unrelated to distributed service addressing. Anycast therefore best matches the described requirement.

Question 286

A service provider wants to control which VPN routes are imported into a customer’s VRF. Which MPLS VPN attribute is primarily used for this purpose?

1. Route Target
2. Route Distinguisher
3. AS Path
4. Router ID

Correct Answer: 1

Explanation

Route Targets determine which VPN routes are imported into or exported from a VRF. They are implemented as extended BGP communities and provide a mechanism for controlling VPN membership and route distribution. For example, a VRF can import routes carrying a specific Route Target while ignoring routes associated with other VPNs. A Route Distinguisher has a different purpose: it makes overlapping prefixes unique in the VPN routing table. AS Path describes autonomous-system traversal, while Router ID identifies a BGP speaker. Route Target is therefore correct for controlling VPN route import and export.

Question 287

A network has several equal-cost paths between leaf and spine switches. The architect wants to use all available paths while avoiding excessive packet reordering. Which design is most appropriate?

1. Per-flow ECMP hashing
2. Per-packet random forwarding
3. STP blocking
4. Static default routing

Correct Answer: 1

Explanation

Per-flow ECMP hashing distributes different traffic flows across available equal-cost paths while maintaining a consistent path for packets belonging to the same flow. Hash inputs can include source and destination addresses and transport-layer ports. Keeping a flow on one path reduces the likelihood of packet reordering while still allowing the network to utilize multiple paths. Per-packet random forwarding can send consecutive packets through different paths and potentially increase reordering. STP blocking would prevent some paths from forwarding, while static default routing does not provide multipath load distribution. Per-flow ECMP is therefore appropriate.

Question 288

An enterprise wants to ensure that a failed route does not remain available in the routing table because the next-hop device is unreachable. Which routing design principle is important?

1. Accurate next-hop reachability detection
2. Increasing VLAN numbers
3. Disabling routing protocols
4. Using larger Ethernet frames

Correct Answer: 1

Explanation

Accurate next-hop reachability detection is important for maintaining correct routing decisions. Routing protocols need to determine whether the next hop and associated forwarding path remain usable. Mechanisms such as BFD, interface tracking, or routing-protocol failure detection can help remove or withdraw routes when connectivity is lost. This prevents traffic from being forwarded toward an unavailable path. VLAN numbering and Ethernet frame size do not determine Layer 3 next-hop reachability. Disabling routing protocols would generally reduce network adaptability. Therefore, reliable next-hop failure detection is an important design principle.

Question 289

A company wants to connect multiple branch sites using Internet links while encrypting traffic between branch routers. Which technology is commonly used to provide the encryption?

1. IPsec
2. STP
3. LACP
4. ARP

Correct Answer: 1

Explanation

IPsec provides authentication, integrity protection, and encryption for IP traffic across an untrusted network such as the public Internet. It is commonly used to build secure site-to-site VPN connections between branch routers, headquarters, data centers, or cloud environments. IPsec can be combined with routing protocols and tunneling technologies depending on the architecture. STP handles Layer 2 loop prevention, LACP aggregates Ethernet links, and ARP resolves IPv4 addresses to MAC addresses. IPsec is therefore the appropriate technology when secure encrypted connectivity is required across Internet-based WAN links.

Question 290

A network administrator wants to classify BGP routes so that the same routing policy can be applied to many prefixes without maintaining individual prefix entries. Which feature is useful?

1. BGP communities
2. STP root priority
3. OSPF router ID
4. Ethernet VLAN tag

Correct Answer: 1

Explanation

BGP communities allow administrators to attach policy-related tags to routes. Instead of maintaining individual policies for every prefix, routes can be grouped according to their community values. Policies can then match those communities and perform actions such as permitting advertisements, changing attributes, or controlling route propagation. This provides a scalable approach to BGP policy management. STP root priority controls spanning-tree elections, OSPF router ID identifies an OSPF router, and VLAN tags identify Layer 2 segments. BGP communities are therefore appropriate for scalable route classification and policy application.

Question 291

A large organization wants to reduce the number of routes advertised from branch networks toward the central data center. Several branch prefixes can safely be represented by a single aggregate. Which technique should be used?

1. Route summarization
2. Packet fragmentation
3. Broadcast replication
4. MAC learning

Correct Answer: 1

Explanation

Route summarization allows multiple specific prefixes to be represented by a single aggregate route. This can reduce routing-table size and decrease the amount of routing information exchanged between branch networks and the central data center. It can also reduce the number of individual route changes propagated through the network. However, the address plan should be designed to support safe aggregation, and administrators must consider potential blackholing if a summary is advertised when some component networks are unavailable. Route summarization therefore provides the desired reduction in routing information.

Question 292

A network architect is designing a data center underlay and wants each leaf to reach every spine using routed point-to-point links. Which protocol type is most appropriate for distributing underlay reachability?

1. IGP
2. DHCP
3. ARP only
4. STP

Correct Answer: 1

Explanation

An Interior Gateway Protocol such as OSPF or IS-IS is commonly used to distribute reachability information across a data center Layer 3 underlay. Routed point-to-point links between leaf and spine switches provide a clean topology in which the IGP can calculate multiple equal-cost paths. ECMP can then use these paths for traffic forwarding. DHCP is used for host addressing, ARP resolves IPv4 addresses at Layer 2, and STP is primarily used for Layer 2 loop prevention. An IGP is therefore appropriate for distributing underlay routing information.

Question 293

An enterprise wants to make sure that traffic destined for a sensitive application passes through a security appliance instead of following the normal shortest path. Which mechanism can accomplish this?

1. Policy-Based Routing
2. ECMP
3. Route summarization
4. BFD

Correct Answer: 1

Explanation

Policy-Based Routing allows forwarding decisions to be based on defined policy criteria rather than only on the destination routing table. Administrators can match specific source networks, destinations, protocols, or other supported attributes and direct matching traffic toward a security appliance. This can be useful for traffic inspection, service insertion, or application-specific forwarding. ECMP distributes traffic across equal-cost paths, route summarization reduces routing information, and BFD detects forwarding failures. PBR therefore provides the necessary mechanism to deliberately steer sensitive application traffic through a particular security device.

Question 294

A service provider needs to support overlapping customer IP addresses on the same PE router. Which design element provides separate customer routing tables?

1. VRF
2. STP
3. LACP
4. HSRP

Correct Answer: 1

Explanation

Virtual Routing and Forwarding creates separate routing tables on the same physical router. Each customer can therefore maintain an independent routing domain, allowing different customers to use overlapping IP address ranges without creating conflicts. In an MPLS Layer 3 VPN architecture, VRFs are commonly associated with customer-facing interfaces and work with MP-BGP to distribute VPN routes between PE routers. STP handles Layer 2 loops, LACP provides link aggregation, and HSRP provides gateway redundancy. VRF is therefore the key design element for customer-specific routing separation.

Question 295

A company has two WAN providers and wants internal routers to prefer one provider for outbound traffic but still retain the other as a backup. Which BGP attribute should be manipulated?

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

Correct Answer: 1

Explanation

Local Preference is commonly used to influence outbound path selection within an autonomous system. The preferred WAN provider can be assigned a higher Local Preference, while routes through the secondary provider receive a lower value. Internal BGP routers will normally prefer the higher Local Preference path. If the preferred path becomes unavailable, the alternative provider can still be selected. MED is generally used to influence inbound path selection by a neighboring AS, while Router ID and origin are considered later in the BGP selection process. Local Preference therefore fits this requirement.

Question 296

A network administrator wants to prevent routing updates from forming an adjacency on a user-facing interface while still allowing normal user traffic through that interface. Which configuration concept is appropriate?

1. Passive interface
2. Route reflector
3. AS-path prepending
4. Route target

Correct Answer: 1

Explanation

A passive interface can prevent a routing protocol from forming neighbor relationships or sending routing protocol updates through a specified interface while allowing normal data traffic to continue. This is useful on user-facing networks where routing adjacencies are not required. It can reduce unnecessary routing-protocol exposure and prevent accidental adjacency formation. Route Reflectors improve BGP scalability, AS-path prepending influences BGP path selection, and Route Targets control VPN route import and export. Therefore, passive-interface configuration is appropriate for suppressing routing protocol communication on a user-facing interface.

Question 297

A data center requires tenant traffic to remain isolated while allowing a shared service network to communicate with multiple tenants. Which architecture can provide this controlled connectivity?

1. VRF segmentation with selective route leaking
2. One unrestricted global routing table
3. One shared Layer 2 broadcast domain
4. Full Layer 2 bridging between tenants

Correct Answer: 1

Explanation

VRF segmentation provides separate routing tables for individual tenants, maintaining logical isolation between their networks. Selective route leaking can then expose only approved shared-service prefixes to the tenants. This approach is useful for services such as DNS, authentication, monitoring, and centralized applications. The shared services can be advertised into multiple tenant VRFs while tenant-specific routes remain isolated. A single global routing table or unrestricted Layer 2 bridging would weaken separation and increase the possibility of unintended communication. VRF segmentation with controlled route leaking therefore provides the required architecture.

Question 298

A BGP administrator wants to influence how a neighboring autonomous system selects between multiple paths toward the same enterprise network. Which attribute can be advertised for this purpose?

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

Correct Answer: 1

Explanation

Multi-Exit Discriminator is a BGP attribute that can be used to influence how a neighboring autonomous system selects among multiple entry points into the advertising AS. A lower MED is generally preferred when comparing otherwise applicable paths from the same neighboring AS. MED is therefore commonly used to communicate an organization’s preference for inbound traffic paths. Local Preference is primarily an internal attribute used within an AS, while Weight is vendor-specific and local to a router. Router ID is primarily used as a BGP identifier and later tie-breaker.

Question 299

An organization wants to ensure that a critical application remains reachable if one physical WAN link fails. Multiple independent links are available between the sites. Which design principle should be applied?

1. Path redundancy
2. Single-homing
3. Route suppression
4. Broadcast extension

Correct Answer: 1

Explanation

Path redundancy provides multiple independent forwarding paths between network locations. If one WAN link fails, traffic can continue through another available path, improving service availability. Routing protocols, ECMP, SD-WAN policies, or other mechanisms can be used to select and manage redundant paths depending on the architecture. Single-homing creates a single physical dependency and therefore increases the impact of a link failure. Route suppression and broadcast extension do not provide physical path redundancy. A redundant WAN design is therefore appropriate for maintaining connectivity to critical applications during individual link failures.

Question 300

A network architect wants to limit the impact of a routing change to a specific part of an OSPF network rather than allowing detailed topology changes to affect every router. Which OSPF design feature helps achieve this?

1. OSPF areas
2. VLAN trunks
3. LACP groups
4. HSRP groups

Correct Answer: 1

Explanation

OSPF areas divide a large routing domain into smaller logical sections. Routers within an area maintain detailed topology information for that area, while summarized information can be exchanged between areas through the OSPF backbone. This hierarchical structure can limit the scope of topology changes and reduce the amount of Link-State Database information that must be processed by every router. VLAN trunks carry Layer 2 VLAN traffic, LACP aggregates physical links, and HSRP provides gateway redundancy. OSPF areas therefore provide the architectural boundary needed to improve routing scalability and contain topology information.