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Question 201

A network architect is designing a data center in which every leaf switch must have connectivity to every spine switch. The goal is predictable latency and multiple equal-cost paths. Which architecture is most appropriate?

1. Three-tier hierarchical
2. Ring topology
3. Leaf-and-spine
4. Hub-and-spoke

Correct Answer: 3

Explanation

A leaf-and-spine architecture provides predictable connectivity and multiple equal-cost paths within a data center. Every leaf switch typically connects to every spine switch, creating a highly connected topology. Traffic between two leaf switches normally travels through one spine switch, and ECMP can distribute traffic across available spine paths. This design provides scalability, consistent latency, and efficient use of available links. Traditional three-tier designs can introduce aggregation bottlenecks, while ring and hub-and-spoke designs generally provide fewer parallel paths. Leaf-and-spine is therefore well suited to modern scalable data center networks.

Question 202

An enterprise wants to prevent unauthorized routes learned from one BGP neighbor from being accepted into its routing table. Which mechanism should be used?

1. Prefix filtering
2. HSRP
3. LACP
4. VXLAN

Correct Answer: 1

Explanation

Prefix filtering allows a network administrator to control which routes are accepted from a BGP neighbor. Prefix lists or route policies can permit approved prefixes and reject unwanted or unexpected advertisements. This is an important security and routing-policy mechanism because it helps prevent accidental or malicious route leaks from affecting the routing table. HSRP provides first-hop redundancy, LACP aggregates links, and VXLAN provides network virtualization. Prefix filtering directly addresses the requirement to control inbound BGP route advertisements.

Question 203

A company needs to connect remote branch offices securely across the public Internet while allowing internal routing protocols to operate through the encrypted connections. Which solution is appropriate?

1. Plain GRE without encryption
2. IPsec VPN
3. STP
4. VLAN trunking

Correct Answer: 2

Explanation

An IPsec VPN provides encryption and authentication for traffic traversing an untrusted network such as the public Internet. It can be combined with appropriate tunneling and routing mechanisms to allow branch networks to exchange routing information securely. IPsec protects the confidentiality and integrity of traffic between VPN endpoints. GRE by itself does not provide encryption, while STP is used for Layer 2 loop prevention and VLAN trunking carries multiple VLANs over Layer 2 links. IPsec VPN is therefore appropriate for secure branch connectivity across the Internet.

Question 204

A BGP network needs to prefer one exit path over another for traffic leaving the autonomous system. Which attribute is commonly used to influence this decision across the internal AS?

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

Correct Answer: 2

Explanation

BGP Local Preference is commonly used to influence outbound traffic within an autonomous system. A higher Local Preference is normally preferred, allowing administrators to designate a preferred exit point for traffic leaving the AS. Because the value is distributed through iBGP, it can consistently influence path selection across multiple internal routers. MED is generally used to influence inbound traffic from a neighboring AS, while Router ID identifies a BGP speaker. Local Preference is therefore appropriate when controlling the preferred outbound path.

Question 205

A service provider wants different customers to use separate routing tables while sharing the same physical PE router. Which combination provides customer-specific routing separation?

1. VRF and MP-BGP
2. STP and LACP
3. HSRP and DHCP
4. NAT and DNS

Correct Answer: 1

Explanation

VRF provides separate customer-specific routing tables on the provider edge router, while MP-BGP can distribute VPN routes between provider edge devices. In an MPLS Layer 3 VPN architecture, VRFs maintain local customer separation and MP-BGP carries VPNv4 or VPNv6 routes across the provider network. Route Distinguishers make overlapping prefixes unique, and Route Targets control route import and export. The other combinations do not provide the required Layer 3 VPN architecture. VRF combined with MP-BGP is therefore appropriate.

Question 206

A network has several equal-cost paths toward the same destination and the architect wants to utilize all available paths rather than keeping only one route. Which capability should be enabled?

1. Route filtering
2. ECMP
3. PBR
4. Route summarization

Correct Answer: 2

Explanation

Equal-Cost Multipath allows a router to install and use multiple routes to the same destination when those routes have equivalent routing costs. ECMP can distribute traffic across the available paths according to the platform’s load-balancing mechanism. This improves bandwidth utilization and provides redundancy if one path fails. Route filtering controls route acceptance or advertisement, PBR applies policy-based forwarding decisions, and route summarization reduces the number of routing entries. ECMP directly addresses the requirement to use multiple equal-cost paths.

Question 207

An organization wants to stop routing updates from a specific interface from entering a routing protocol while still allowing the interface to remain operational. Which design technique is appropriate?

1. Passive interface
2. NAT overload
3. EtherChannel
4. Anycast

Correct Answer: 1

Explanation

A passive interface can prevent a routing protocol from forming neighbor relationships or sending routing protocol updates through a particular interface while allowing the interface itself to remain operational for normal data traffic. This is useful on user-facing or infrastructure interfaces where routing adjacencies are not required. NAT overload translates multiple private addresses, EtherChannel aggregates physical links, and Anycast allows multiple locations to advertise the same address. A passive interface is therefore the appropriate design technique for suppressing routing protocol communication on a selected interface.

Question 208

A data center requires a control plane capable of advertising MAC and IP reachability information for VXLAN segments. Which technology is commonly used with VXLAN for this purpose?

1. EVPN
2. DHCP
3. HSRP
4. NAT

Correct Answer: 1

Explanation

Ethernet VPN, commonly implemented with MP-BGP, provides a control plane for VXLAN environments. EVPN can advertise MAC and IP reachability information between VXLAN tunnel endpoints, reducing reliance on data-plane learning alone. This combination allows scalable Layer 2 and Layer 3 network virtualization across a Layer 3 underlay. DHCP provides host configuration, HSRP provides first-hop redundancy, and NAT translates addresses. EVPN is therefore commonly paired with VXLAN to provide scalable control-plane learning and traffic forwarding information.

Question 209

An enterprise needs to make routing decisions based on the source IP address of traffic rather than only the destination prefix. Which forwarding method should be considered?

1. ECMP
2. PBR
3. Route summarization
4. BFD

Correct Answer: 2

Explanation

Policy-Based Routing allows forwarding decisions to use criteria beyond the destination routing table. Policies can match source addresses, destination addresses, protocols, ports, or other supported attributes and then specify a particular next hop or interface. This makes PBR useful for directing traffic from specific departments, applications, or source networks through security appliances or preferred WAN links. ECMP uses multiple equal-cost routes, route summarization aggregates prefixes, and BFD detects forwarding failures. PBR is therefore appropriate when source-based forwarding decisions are required.

Question 210

A network architect wants to minimize the impact of a routing failure in one geographic region so that other regions continue operating normally. Which design principle is most appropriate?

1. Failure-domain isolation
2. Single-path routing
3. Large Layer 2 domains
4. Centralized forwarding

Correct Answer: 1

Explanation

Failure-domain isolation limits the geographic or logical scope of failures. By dividing a network into appropriate routing domains, areas, regions, or other controlled boundaries, a failure in one section can be prevented from unnecessarily affecting the entire network. This can reduce the amount of routing information affected and improve operational stability. Single-path routing creates dependencies, large Layer 2 domains can increase failure propagation, and centralized forwarding may create a single point of failure. Failure-domain isolation is therefore an important design principle for resilient large-scale networks.

Question 211

A company wants to advertise several internal networks as one aggregate prefix toward an external BGP provider. What is the primary benefit of this approach?

1. Increased broadcast traffic
2. Reduced routing information
3. Elimination of BGP
4. Removal of all routing policies

Correct Answer: 2

Explanation

Advertising an aggregate prefix can reduce the amount of routing information exchanged with an external provider. Instead of advertising numerous specific prefixes, the organization can advertise a summarized route when the addressing plan supports safe aggregation. This reduces routing-table size and can improve scalability. However, aggregation must be designed carefully because overly broad summaries can attract traffic for destinations that are not actually reachable. It does not eliminate BGP or routing policies. The primary benefit is reduction of routing information and improved scalability.

Question 212

An enterprise has two Internet connections and wants to prefer one provider for outbound traffic while keeping the second provider available as a backup. Which BGP mechanism is commonly used internally?

1. Local Preference
2. MED only
3. Router ID
4. AS-path padding only

Correct Answer: 1

Explanation

Local Preference is commonly used to control outbound path selection within an autonomous system. The preferred provider can be assigned a higher Local Preference, causing internal BGP routers to prefer that path. The secondary provider can have a lower value and remain available as an alternative. MED can influence path selection by a neighboring AS, but it is not the primary internal attribute for this requirement. Router ID identifies the BGP speaker, while AS-path manipulation is more commonly used to influence inbound traffic. Local Preference is therefore appropriate for this outbound policy.

Question 213

A network designer wants to provide gateway redundancy for hosts in a VLAN without requiring hosts to know which physical router is currently forwarding traffic. Which technology should be used?

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

Correct Answer: 2

Explanation

Hot Standby Router Protocol provides first-hop gateway redundancy. Multiple routers can participate in an HSRP group while hosts use a shared virtual IP address as their default gateway. One router normally forwards traffic while another remains available to take over if the active device fails. This allows endpoint configuration to remain unchanged during a gateway failure. BGP provides interdomain routing, VXLAN provides network virtualization, and BFD detects forwarding failures. HSRP directly addresses the requirement for redundant default-gateway services.

Question 214

A service provider wants to prevent customer routes from being accidentally leaked between two separate VPNs. Which mechanism provides control over VPN route import and export?

1. Route Targets
2. Router IDs
3. Ethernet MTU
4. MAC addresses

Correct Answer: 1

Explanation

Route Targets control VPN route import and export between VRFs in an MPLS Layer 3 VPN environment. By assigning appropriate route-target communities, the provider can determine which VPN routes are imported into each customer’s VRF. This allows separate VPNs to remain isolated while also supporting controlled inter-VPN connectivity when required. Route Distinguishers provide route uniqueness but do not directly define route import and export policy. Router IDs, MTU values, and MAC addresses do not provide this VPN membership control. Route Targets are therefore the appropriate mechanism.

Question 215

A company needs to connect two switches using multiple physical Ethernet links and wants the links to operate as a single logical connection. Which protocol is appropriate for dynamic link aggregation?

1. OSPF
2. LACP
3. BGP
4. BFD

Correct Answer: 2

Explanation

Link Aggregation Control Protocol dynamically negotiates and maintains an EtherChannel between compatible devices. Multiple physical Ethernet links are combined into a logical port-channel, providing redundancy and potentially increased aggregate bandwidth. If one member link fails, traffic can continue through the remaining active members. OSPF and BGP are routing protocols, while BFD is designed for rapid failure detection. LACP is therefore the appropriate protocol when dynamic Ethernet link aggregation is required.

Question 216

A network administrator needs to prevent a routing protocol from advertising a specific set of prefixes to a neighbor while continuing to advertise other permitted routes. Which tool is commonly used?

1. Prefix list
2. DHCP scope
3. VLAN database
4. MAC address table

Correct Answer: 1

Explanation

A prefix list provides precise control over IPv4 or IPv6 prefixes used in routing policies. It can permit or deny specific prefixes or prefix ranges and can be applied to routing protocol policies such as BGP. This makes prefix lists useful for controlling route advertisements and preventing unwanted prefixes from being exchanged with neighbors. DHCP scopes assign host addresses, VLAN databases maintain VLAN information, and MAC address tables map Layer 2 addresses to interfaces. A prefix list is therefore appropriate for selective route filtering.

Question 217

An organization is deploying a WAN with MPLS, broadband, and LTE links and wants applications to dynamically use the path that meets predefined performance requirements. Which solution best supports this requirement?

1. SD-WAN
2. STP
3. Static NAT
4. Traditional Layer 2 switching

Correct Answer: 1

Explanation

SD-WAN can integrate multiple WAN transports and apply centralized policies to determine how application traffic should use those connections. Performance measurements such as latency, jitter, packet loss, and availability can be used by supported implementations to influence path selection. This allows organizations to use MPLS, Internet, LTE, and other transports according to application and business requirements. STP is designed for Layer 2 loop prevention, NAT handles address translation, and traditional Layer 2 switching does not provide centralized application-aware WAN path selection. SD-WAN directly addresses this scenario.

Question 218

A BGP administrator wants to attach policy information to routes so that downstream routers can apply specific routing decisions based on that information. Which BGP feature should be used?

1. BGP Communities
2. Router ID
3. TCP window size
4. Ethernet VLAN ID

Correct Answer: 1

Explanation

BGP communities allow routes to be tagged with policy information that can be interpreted by other BGP-speaking devices. Administrators can use standard or extended communities to implement policies such as controlling route advertisement, identifying customer routes, or influencing routing behavior. Communities provide a scalable way to communicate routing-policy intent without creating numerous individual prefix-based policies. Router ID identifies the BGP speaker, TCP window size affects transport behavior, and VLAN IDs identify Layer 2 segments. BGP communities are therefore appropriate for carrying routing-policy information with routes.

Question 219

A network has a requirement for fast detection of a failed path between directly connected routers. The routing protocol itself has relatively slow convergence timers. Which technology can be integrated to improve detection speed?

1. DNS
2. BFD
3. NAT
4. ARP

Correct Answer: 2

Explanation

BFD provides rapid bidirectional failure detection between network devices. It can operate independently of the normal routing protocol hello and dead timers and notify the routing protocol when the forwarding path becomes unavailable. This allows the routing protocol to react more quickly without necessarily using extremely aggressive protocol timers. DNS resolves hostnames, NAT translates addresses, and ARP resolves IPv4 addresses to Layer 2 addresses. BFD is therefore the appropriate technology for improving failure detection and accelerating routing convergence.

Question 220

A network architect needs to connect multiple data center locations while maintaining Layer 3 routing between sites and avoiding unnecessary extension of large Layer 2 broadcast domains. Which design approach is generally appropriate?

1. Large stretched Layer 2 domain everywhere
2. Layer 3 inter-site connectivity
3. Single Layer 2 switch between all sites
4. Disabling routing between locations

Correct Answer: 2

Explanation

Layer 3 inter-site connectivity provides routing between data center locations without requiring large Layer 2 broadcast domains to span the entire environment. This approach can improve scalability, fault isolation, and operational control. Each site can maintain its own Layer 2 domains while routers or Layer 3 switches provide connectivity between locations. Large stretched Layer 2 domains can increase the scope of broadcast traffic and certain failure conditions. A Layer 3 inter-site architecture therefore provides a scalable approach for connecting multiple data center locations.