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Q261. Which OSPF area type blocks Type 5 LSAs and uses a default route to reach external destinations?

1) Standard area
2) Stub area
3) NSSA
4) Backbone area

Correct Answer: 2) Stub area

Explanation:
An OSPF stub area is designed to reduce the amount of routing information that an area must maintain. Type 5 LSAs, which normally describe external routes redistributed into OSPF, are not permitted inside a stub area. Instead, an Area Border Router (ABR) normally advertises a default route into the stub area so that internal routers can forward unknown external destinations toward the ABR. This reduces the size of the link-state database and routing table while maintaining connectivity to external networks. Stub areas are useful when detailed external route information is unnecessary for the routers located inside the area.

Q262. Which OSPF area type suppresses both external routes and inter-area summary routes, except for a default route?

1) Totally stubby area
2) NSSA
3) Standard area
4) Backbone area

Correct Answer: 1) Totally stubby area

Explanation:
A totally stubby area is a Cisco implementation designed to minimize routing information inside an OSPF area. It blocks external Type 5 LSAs and inter-area Type 3 and Type 4 LSAs, while the ABR provides a default route for destinations outside the area. This means routers within the area do not need detailed information about external networks or routes in other OSPF areas. The design can significantly reduce the size of the link-state database and simplify routing decisions. It is particularly useful for remote or branch areas where the routers primarily need a path toward the rest of the network.

Q263. An administrator wants an OSPF router to advertise a summary route instead of multiple specific prefixes. Which feature should be considered?

1) OSPF route summarization
2) OSPF authentication
3) OSPF passive interface
4) OSPF neighbor priority

Correct Answer: 1) OSPF route summarization

Explanation:
OSPF route summarization allows multiple specific routes to be represented by a larger summary prefix, reducing routing information exchanged between areas. Inter-area summarization is normally performed on an Area Border Router (ABR), while external route summarization can be performed on an Autonomous System Boundary Router (ASBR). Proper summarization can reduce routing table size and limit the propagation of topology changes. It is important to ensure that the summary accurately represents the intended address space. Poorly designed summaries can create undesirable routing behavior, so administrators should understand the underlying prefixes before implementing route aggregation.

Q264. Which EIGRP feature is available in named configuration mode and organizes configuration by address family?

1) EIGRP named mode
2) EIGRP stub mode
3) EIGRP passive mode
4) EIGRP redistribution mode

Correct Answer: 1) EIGRP named mode

Explanation:
EIGRP named mode provides a more structured configuration approach compared with the traditional autonomous-system-number configuration. The configuration is organized into sections such as address-family configuration and topology configuration. This structure makes it easier to manage EIGRP features, particularly in environments supporting IPv4 and IPv6. Named mode also provides additional configuration capabilities and a consistent hierarchy for advanced EIGRP settings. Administrators should understand the distinction between the traditional EIGRP configuration and named mode because the commands and configuration structure differ. Named mode is especially useful when maintaining larger networks with multiple address families.

Q265. Which command is commonly used to verify EIGRP topology information and identify successor and feasible successor routes?

1) show ip eigrp topology
2) show ip ospf database
3) show ip bgp topology
4) show eigrp routes

Correct Answer: 1) show ip eigrp topology

Explanation:
The show ip eigrp topology command provides detailed information about routes known to EIGRP. It can show the feasible distance, reported distance, successor information, and feasible successors when they exist. This makes the command especially valuable when troubleshooting EIGRP route selection and backup paths. Administrators can use the output to determine whether the feasibility condition is satisfied and whether an alternate route is immediately available. The command is different from show ip route, which primarily displays routes installed in the routing table rather than the complete EIGRP topology information maintained by the routing process.

Q266. What is one major benefit of EIGRP route summarization at a network boundary?

1) It increases broadcast traffic
2) It reduces routing table size and limits topology changes
3) It disables all EIGRP authentication
4) It converts EIGRP into OSPF

Correct Answer: 2) It reduces routing table size and limits topology changes

Explanation:
EIGRP summarization can significantly improve scalability by allowing several specific prefixes to be represented by one summary route. This reduces the amount of routing information that neighboring routers need to maintain. Another important benefit is that topology changes inside the summarized region may not need to propagate beyond the summarization boundary as long as the summary remains valid. This can reduce query propagation and help prevent unnecessary EIGRP convergence activity. Summarization is therefore valuable in larger networks, particularly at distribution or branch boundaries where many detailed prefixes can otherwise increase routing complexity.

Q267. Which BGP attribute is generally preferred when a router selects among paths learned from different external autonomous systems and wants to influence inbound traffic?

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

Correct Answer: 2) MED

Explanation:
The Multi-Exit Discriminator (MED) is a BGP attribute that can be used to influence how another autonomous system selects an entry point into the local autonomous system. A lower MED is generally preferred when comparing otherwise suitable paths from the same neighboring autonomous system. MED is therefore commonly used to influence inbound traffic, while Local Preference is normally used to influence outbound path selection within the local AS. MED should not be confused with Weight, which is a Cisco-specific attribute that is locally significant to one router. Route maps can be used to modify MED for selected routes.

Q268. Which BGP feature allows an administrator to apply different routing policies to routes based on matching conditions?

1) Route map
2) HSRP tracking
3) NHRP shortcut
4) LDP discovery

Correct Answer: 1) Route map

Explanation:
BGP route maps provide a flexible method for applying routing policies to selected prefixes or paths. A route map can use match statements to identify routes based on characteristics such as prefix lists, communities, or AS-path information. Set statements can then modify attributes such as Local Preference, MED, Weight, or communities. Route maps can be applied to BGP neighbors for inbound or outbound policy control. This makes them a fundamental tool for implementing sophisticated BGP policies. Because route maps are processed sequentially, administrators should carefully design their sequence numbers and ensure that unmatched routes receive the intended default behavior.

Q269. Which command is useful for determining whether a BGP neighbor relationship is established and how many prefixes have been received?

1) show ip bgp summary
2) show ip ospf interface
3) show ip eigrp topology
4) show mpls interfaces

Correct Answer: 1) show ip bgp summary

Explanation:
The show ip bgp summary command provides a concise overview of BGP neighbor relationships and is one of the most useful commands for initial BGP troubleshooting. It displays information such as the BGP neighbor address, autonomous system, message counters, uptime, and the state or number of prefixes received. If the state column contains a number rather than a word such as Idle or Active, the BGP session is generally established and that number represents prefixes received from the neighbor. This command gives administrators a quick way to determine whether BGP sessions are operating as expected.

Q270. In an MPLS Layer 3 VPN, which protocol is commonly used between PE routers to exchange VPNv4 routes?

1) OSPF
2) EIGRP
3) MP-BGP
4) NHRP

Correct Answer: 3) MP-BGP

Explanation:
Multiprotocol BGP (MP-BGP) is commonly used between Provider Edge routers to exchange VPNv4 or VPNv6 routes in an MPLS Layer 3 VPN. MP-BGP carries customer VPN routes along with important attributes such as Route Distinguishers and Route Targets. The Route Distinguisher makes otherwise overlapping customer prefixes unique in the provider network, while Route Targets determine which VRFs import or export those routes. The provider core routers do not generally need customer-specific routing information. Instead, MPLS labels and the provider’s internal routing protocol allow packets to travel between the appropriate PE routers.

Q271. Which MPLS router normally forwards labeled packets through the provider core without maintaining customer VRF information?

1) CE router
2) PE router
3) P router
4) Route Reflector

Correct Answer: 3) P router

Explanation:
A Provider (P) router operates inside the MPLS service-provider core and primarily forwards packets based on labels. Unlike PE routers, P routers generally do not maintain individual customer VRFs or customer-specific VPN routing tables. This separation is one of the reasons MPLS Layer 3 VPNs can scale efficiently. The PE routers handle customer connectivity and VPN route information, while P routers provide high-speed core transport. Keeping customer-specific information out of the provider core reduces the amount of routing information that core routers must process and simplifies the architecture of large MPLS networks.

Q272. What is the primary purpose of a VRF in an MPLS Layer 3 VPN environment?

1) To provide separate routing tables for different VPNs
2) To increase Ethernet frame size
3) To replace BGP entirely
4) To encrypt customer traffic

Correct Answer: 1) To provide separate routing tables for different VPNs

Explanation:
Virtual Routing and Forwarding (VRF) allows a router to maintain multiple independent routing tables on the same physical device. In MPLS Layer 3 VPNs, each customer or VPN can have its own VRF, preventing overlapping private IP address spaces from causing conflicts. A PE router associates customer-facing interfaces with the appropriate VRF and uses that VRF when forwarding traffic. VRFs provide logical separation but do not themselves encrypt traffic. MPLS VPN labels and MP-BGP are used together with VRFs to transport and identify customer traffic across the provider network while maintaining separation between different VPNs.

Q273. Which DMVPN phase uses NHRP redirect messages and NHRP shortcuts to improve spoke-to-spoke communication?

1) Phase 1
2) Phase 2
3) Phase 3
4) Phase 0

Correct Answer: 3) Phase 3

Explanation:
DMVPN Phase 3 introduces NHRP redirect and shortcut mechanisms to improve scalability and routing efficiency. When traffic initially travels through the hub even though a direct spoke-to-spoke path is possible, the hub can send an NHRP redirect to inform the spoke that a better path exists. The spoke can then use NHRP to resolve the appropriate remote spoke and establish a more direct forwarding path. Phase 3 is particularly useful in large hub-and-spoke deployments because it provides more flexible routing behavior than earlier DMVPN phases while reducing unnecessary traffic through the hub.

Q274. Which protocol is commonly used by FlexVPN for secure tunnel establishment and key management?

1) IKEv2
2) FTP
3) ARP
4) LDP

Correct Answer: 1) IKEv2

Explanation:
FlexVPN commonly uses Internet Key Exchange version 2 (IKEv2) as its framework for establishing secure IPsec tunnels and negotiating security parameters. IKEv2 provides mechanisms for authentication, security association negotiation, and key management. FlexVPN can support different VPN topologies and is designed to provide a consistent configuration model across various deployment scenarios. After the IKEv2 negotiation establishes the necessary security associations, IPsec can protect the actual data traffic. Understanding the relationship between IKEv2 and IPsec is important when troubleshooting FlexVPN because IKEv2 handles negotiation and management while IPsec provides data-plane protection.

Q275. Which QoS mechanism provides strict priority treatment for delay-sensitive traffic such as voice?

1) WRED
2) LLQ
3) FIFO
4) CB marking

Correct Answer: 2) LLQ

Explanation:
Low Latency Queuing (LLQ) provides a strict priority queue for delay-sensitive traffic, making it particularly useful for voice and other real-time applications. LLQ is implemented as part of a class-based QoS policy and gives the priority class preferential treatment during congestion. This helps reduce delay and jitter for traffic that is sensitive to transmission timing. However, the priority queue should be configured carefully because excessive priority traffic can potentially starve other classes. Bandwidth limits and proper traffic classification are therefore important. LLQ is different from ordinary CBWFQ because it provides strict priority rather than only guaranteed bandwidth allocation.

Q276. What is the main difference between QoS policing and shaping?

1) Policing buffers excess traffic while shaping always drops it
2) Shaping can buffer excess traffic, while policing can drop or remark it
3) Both mechanisms always encrypt traffic
4) Shaping operates only on routing protocols

Correct Answer: 2) Shaping can buffer excess traffic, while policing can drop or remark it

Explanation:
QoS policing and shaping both control traffic rates, but they handle excess traffic differently. A policer typically examines traffic against a configured rate and may drop or remark packets that exceed the allowed rate. Shaping, on the other hand, can place excess packets into a queue and transmit them later when bandwidth becomes available. This makes shaping useful for smoothing traffic toward a service-provider rate. Policing is more appropriate when strict rate enforcement is required. Understanding this difference is important because choosing policing when buffering is needed can result in packet loss, while shaping may introduce additional delay because packets can wait in the queue.

Q277. Which protocol feature allows IPv6 hosts to automatically configure addresses using information received from routers?

1) SLAAC
2) ARP
3) NAT
4) NHRP

Correct Answer: 1) SLAAC

Explanation:
Stateless Address Autoconfiguration (SLAAC) allows IPv6 hosts to automatically generate addresses using information advertised by routers through Router Advertisement messages. The router advertises an IPv6 prefix, and the host combines that prefix with an interface identifier or other address-generation mechanism. SLAAC reduces the need for a centralized DHCP server for basic address configuration. IPv6 Neighbor Discovery provides the mechanisms used by hosts and routers to exchange these messages. SLAAC can also operate alongside DHCPv6 when additional configuration information is required. It is therefore an important component of modern IPv6 network deployment and troubleshooting.

Q278. Which IPv6 message is used by a host to discover routers on its local network?

1) Router Solicitation
2) Neighbor Advertisement
3) Echo Reply
4) DHCP Discover

Correct Answer: 1) Router Solicitation

Explanation:
An IPv6 host can send a Router Solicitation (RS) message to request Router Advertisement information from routers on the local link. The router responds with a Router Advertisement containing information such as prefixes, default-router information, and autoconfiguration flags. This process is part of IPv6 Neighbor Discovery and uses ICMPv6. Router Solicitation is especially useful when a host needs router information without waiting for the next periodic Router Advertisement. Neighbor Solicitation and Neighbor Advertisement serve different purposes, including address resolution and neighbor reachability functions. Understanding these ICMPv6 message types is essential for IPv6 troubleshooting.

Q279. Which command is most useful for verifying the IP SLA operation configuration and current status?

1) show ip sla statistics
2) show ip bgp vpnv4
3) show ip ospf virtual-link
4) show mpls ldp discovery

Correct Answer: 1) show ip sla statistics

Explanation:
The show ip sla statistics command provides information about configured IP SLA operations and their collected results. It can help administrators determine whether an operation is succeeding or failing and review measured performance information depending on the type of probe. This is particularly useful when IP SLA is combined with object tracking for redundant routing. If an IP SLA probe fails repeatedly, the associated tracked object can change state and trigger a routing decision. During troubleshooting, administrators should verify both the SLA statistics and the tracking configuration to determine whether a route change is caused by an actual reachability failure.

Q280. Which command is commonly used to verify the HSRP state and active/standby roles of a router?

1) show standby
2) show ip eigrp topology
3) show ip bgp summary
4) show crypto ikev2 sa

Correct Answer: 1) show standby

Explanation:
The show standby command is commonly used to examine HSRP operation and determine the current state of the router. The output can identify whether the router is Active, Standby, or in another HSRP state, along with information about the virtual IP address, configured priority, preemption, and timers. This command is useful when troubleshooting first-hop redundancy problems. Administrators can compare the output on multiple HSRP routers to determine which router currently owns the active role and whether priority or tracking has influenced the election. It is one of the fundamental verification commands for HSRP deployments.