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Q81. Which command displays detailed information about OSPF-enabled interfaces?

1) show ip ospf interface
2) show ip ospf database
3) show ip route ospf
4) show ospf neighbors

Correct Answer: 1) show ip ospf interface

Explanation: The show ip ospf interface command provides detailed information about interfaces participating in OSPF. The output includes the OSPF process ID, area, interface cost, network type, timers, priority, designated router information, and neighbor details. This command is especially useful when troubleshooting OSPF adjacency or route-selection problems because it allows an administrator to verify whether interface-level settings match the intended configuration. For example, mismatched hello or dead timers, incorrect network types, or unexpected interface costs can affect OSPF operation. Reviewing this output is an important step when diagnosing OSPF behavior.

Q82. Which OSPF network type normally elects a designated router and backup designated router?

1) Point-to-point
2) Broadcast
3) Loopback
4) Point-to-multipoint

Correct Answer: 2) Broadcast

Explanation: OSPF broadcast network types, commonly associated with Ethernet interfaces, elect a Designated Router (DR) and Backup Designated Router (BDR). The DR reduces the number of OSPF adjacencies required on a multi-access network and helps control the amount of LSA flooding. The BDR provides redundancy if the DR fails. OSPF uses interface priority and router ID as part of the election process. Point-to-point networks do not require a DR or BDR because only two routers participate on the link. Understanding DR and BDR behavior is important when troubleshooting OSPF adjacency formation on Ethernet networks.

Q83. Which EIGRP command displays the topology table?

1) show ip eigrp topology
2) show ip eigrp neighbors
3) show ip route eigrp
4) show eigrp database

Correct Answer: 1) show ip eigrp topology

Explanation: The show ip eigrp topology command displays information from the EIGRP topology table. It can show successor routes, feasible successors, feasible distances, reported distances, and other information used by EIGRP’s route-selection process. This command is especially helpful when investigating why a particular EIGRP route is or is not being installed in the routing table. The neighbor table and topology table serve different purposes: show ip eigrp neighbors focuses on EIGRP adjacencies, while show ip eigrp topology focuses on routes and their path information. Both are valuable troubleshooting commands.

Q84. What happens when an EIGRP successor route fails and a feasible successor is available?

1) EIGRP immediately removes the destination permanently
2) EIGRP performs a full network reload
3) The feasible successor can become the new successor
4) EIGRP changes the AS number

Correct Answer: 3) The feasible successor can become the new successor

Explanation: When an EIGRP successor route becomes unavailable, EIGRP can quickly install a feasible successor as the new successor if one is available. Because the feasible successor has already satisfied the feasibility condition, EIGRP can use it without first performing a complete route recomputation. This contributes to EIGRP’s rapid convergence. If no feasible successor exists, EIGRP may need to query neighbors for an alternative path. Therefore, maintaining redundant paths that satisfy the feasibility condition can significantly improve network resilience and reduce convergence time when a primary path fails.

Q85. Which BGP attribute is considered a well-known mandatory attribute?

1) Local Preference
2) MED
3) AS_PATH
4) Weight

Correct Answer: 3) AS_PATH

Explanation: AS_PATH is a well-known mandatory BGP attribute. It records the autonomous systems through which a BGP route has passed and is included with route advertisements. BGP uses AS_PATH for path selection, and it also provides an important mechanism for preventing routing loops because a router can reject a route if its own AS number already appears in the path. Other BGP attributes have different classifications and purposes. Understanding BGP attribute categories helps administrators troubleshoot route advertisements and determine why a particular path is selected over another path.

Q86. Which BGP attribute is locally significant and is not advertised to external BGP peers?

1) Weight
2) AS_PATH
3) Origin
4) MED

Correct Answer: 1) Weight

Explanation: Weight is a Cisco-specific BGP path-selection attribute that has local significance to a single router. It is not advertised to other BGP neighbors. When multiple paths exist, a higher weight is preferred by the router. Because weight is local, it can be useful when an administrator wants one particular router to prefer a specific BGP path without influencing other routers in the autonomous system. Weight has higher local importance than many other BGP attributes in Cisco’s path-selection process. It should therefore be used carefully when implementing local outbound routing policies.

Q87. Which command provides a summary of BGP neighbor relationships?

1) show ip bgp routes
2) show ip bgp summary
3) show ip route bgp
4) show bgp interfaces

Correct Answer: 2) show ip bgp summary

Explanation: The show ip bgp summary command provides a concise overview of BGP operation and neighbor relationships. It typically displays the local BGP router ID, local AS number, BGP table information, neighbor IP addresses, remote AS numbers, message statistics, and the current state or number of prefixes received from each neighbor. This command is one of the first commands administrators use when troubleshooting BGP sessions. If a neighbor is not established, the output can provide clues about whether the session is active, idle, or otherwise failing. More detailed information can then be obtained with other BGP commands.

Q88. In an MPLS Layer 3 VPN, which device normally connects directly to the customer edge router?

1) P router
2) PE router
3) Route reflector only
4) LDP server

Correct Answer: 2) PE router

Explanation: The Provider Edge, or PE, router normally connects directly to the Customer Edge, or CE, router in an MPLS Layer 3 VPN architecture. The PE maintains customer VRFs and participates in the provider’s VPN control plane. The CE generally exchanges routes with the PE using a routing protocol such as BGP, OSPF, EIGRP, or static routing. Provider core, or P, routers normally do not maintain customer VRF information. They provide MPLS transport across the provider network. This separation allows the provider core to carry VPN traffic efficiently without maintaining individual customer routing tables.

Q89. What is the primary purpose of a VRF Route Target?

1) To define the OSPF router ID
2) To control which VPN routes are imported or exported
3) To assign an IP address to the CE
4) To calculate the interface bandwidth

Correct Answer: 2) To control which VPN routes are imported or exported

Explanation: Route Targets control the distribution of VPN routes between VRFs in an MPLS Layer 3 VPN environment. An export Route Target is attached to routes when they are advertised into the VPN control plane. A VRF can then use import Route Target values to determine which VPN routes should be installed locally. This provides flexible control over VPN connectivity and allows providers to create different customer topologies. Route Targets are different from Route Distinguishers. The RD provides uniqueness for overlapping prefixes, while the RT determines which VPN routes are allowed into or out of a VRF.

Q90. Which DMVPN phase supports dynamic spoke-to-spoke tunnels?

1) Phase 1 only
2) Phase 2
3) Phase 0 only
4) No DMVPN phase supports them

Correct Answer: 2) Phase 2

Explanation: DMVPN Phase 2 supports dynamic spoke-to-spoke tunnel establishment. In this design, spokes can use NHRP to discover the NBMA address of another spoke and then establish a direct GRE/IPsec tunnel. This reduces the need to send all spoke-to-spoke traffic through the hub. Phase 1 generally uses a hub-and-spoke model in which spoke traffic passes through the hub. Phase 2 improves forwarding efficiency by allowing direct spoke communication while retaining the dynamic characteristics of DMVPN. Proper NHRP operation and compatible routing behavior are essential for successful Phase 2 deployments.

Q91. Which protocol is responsible for resolving a DMVPN tunnel address to an NBMA address?

1) NHRP
2) STP
3) LACP
4) DHCP

Correct Answer: 1) NHRP

Explanation: Next Hop Resolution Protocol, or NHRP, resolves logical tunnel addresses to the underlying NBMA addresses used by DMVPN peers. This capability allows DMVPN routers to dynamically discover where another peer is located on the physical or underlying network. The hub maintains information about registered spokes, while spokes can obtain information about other peers as required. NHRP is therefore central to dynamic DMVPN operation. Administrators can use commands such as show ip nhrp to inspect mappings and registrations when troubleshooting DMVPN connectivity, especially when direct spoke-to-spoke communication is not functioning correctly.

Q92. Which QoS mechanism can randomly drop packets before a queue becomes completely full?

1) LLQ
2) WRED
3) CBWFQ
4) FIFO

Correct Answer: 2) WRED

Explanation: Weighted Random Early Detection, or WRED, is a congestion-avoidance mechanism that can begin dropping packets before a queue reaches its maximum capacity. By detecting increasing congestion early, WRED helps reduce the likelihood of tail drops and can encourage TCP sources to reduce their transmission rates. WRED can use different thresholds based on traffic characteristics and IP precedence or DSCP markings. It is most useful for traffic that responds appropriately to packet loss, particularly TCP traffic. WRED differs from queueing mechanisms such as LLQ and CBWFQ because its primary purpose is congestion avoidance rather than scheduling traffic.

Q93. What is the purpose of a QoS service policy applied to an interface?

1) To define how classified traffic is handled
2) To disable routing protocols
3) To assign a router ID
4) To create a VRF automatically

Correct Answer: 1) To define how classified traffic is handled

Explanation: A QoS service policy applies a configured policy map to traffic entering or leaving an interface. The policy can classify traffic and then perform actions such as marking, queuing, shaping, policing, or congestion management. The policy is normally created using class maps and policy maps and then applied with the service-policy command. This provides administrators with granular control over how different applications or traffic classes are treated. Correct classification is essential because the QoS actions are applied based on the traffic matching the configured class criteria. Proper direction, interface, and policy configuration are also important.

Q94. Which NAT type allows multiple internal hosts to share one public IPv4 address by using different port numbers?

1) Static NAT
2) Dynamic NAT without overload
3) PAT
4) Static routing

Correct Answer: 3) PAT

Explanation: Port Address Translation, commonly called PAT or NAT overload, allows multiple internal hosts to share a single public IPv4 address. PAT distinguishes individual connections by using different TCP or UDP port numbers along with the translated address. This greatly increases the number of private hosts that can access external networks using a limited number of public IPv4 addresses. PAT is widely used in enterprise and home networks because public IPv4 addresses are limited. When troubleshooting PAT, administrators should verify the inside and outside interface designations, translation rules, access lists, routing, and the active translation table.

Q95. Which command can be used to clear dynamic NAT translations?

1) clear ip nat translation *
2) reset nat all
3) delete ip nat table
4) clear ip route nat

**Correct Answer: 1) clear ip nat translation **

Explanation: The clear ip nat translation * command removes dynamic NAT translation entries from the router’s NAT translation table. This can be useful during troubleshooting or testing when an administrator needs to force new translations to be created. Clearing translations can temporarily interrupt active sessions because existing translation information is removed. For that reason, the command should be used carefully on production networks. Administrators can first inspect the translation table with show ip nat translations and NAT statistics with show ip nat statistics before deciding whether clearing the entries is necessary.

Q96. Which IPsec protocol provides encryption and authentication for IP packet payloads?

1) ESP
2) ARP
3) ICMP
4) GRE

Correct Answer: 1) ESP

Explanation: Encapsulating Security Payload, or ESP, is an IPsec protocol that can provide confidentiality through encryption as well as integrity and authentication. ESP is widely used for site-to-site and remote-access VPN implementations. Authentication and encryption algorithms are negotiated through the security association process, often using IKE or IKEv2. GRE itself does not provide encryption, although GRE can be combined with IPsec to protect GRE tunnels. When troubleshooting an IPsec VPN, administrators should examine both the IKE security association and the IPsec security association because successful key negotiation does not always guarantee that protected data traffic is being transmitted correctly.

Q97. Which command is commonly used to verify IPsec security associations?

1) show crypto ipsec sa
2) show ipsec routes
3) show crypto tunnel table
4) show security ipsec only

Correct Answer: 1) show crypto ipsec sa

Explanation: The show crypto ipsec sa command displays information about IPsec security associations and traffic protected by IPsec. It can provide details such as local and remote proxy identities, encryption and authentication parameters, packet counters, and encapsulation or decapsulation statistics. These counters are especially useful when troubleshooting because they can indicate whether traffic is actually being encrypted and decrypted. If IKE negotiation succeeds but IPsec packet counters remain unchanged, administrators should investigate traffic selectors, routing, access lists, or other configuration issues. This command is therefore an important part of systematic IPsec troubleshooting.

Q98. What is the purpose of a route map in Cisco routing configuration?

1) To provide physical cable connectivity
2) To apply conditional routing policies
3) To replace all routing protocols
4) To assign switch VLAN numbers

Correct Answer: 2) To apply conditional routing policies

Explanation: A route map allows administrators to create conditional routing policies by matching specific route or packet characteristics and applying defined actions. Route maps are commonly used with route redistribution, policy-based routing, BGP policies, and route filtering. Match statements identify traffic or routes, while set statements determine what action should be taken, such as changing an attribute, modifying the next hop, or assigning a metric. Route maps are processed sequentially, so their order and match conditions are important. Careful design is necessary to avoid unintentionally permitting, denying, or modifying routes.

Q99. Which command displays routes learned through OSPF in the IPv4 routing table?

1) show ip route ospf
2) show ip ospf routes only
3) show ospf database routes
4) show route protocol ospf

Correct Answer: 1) show ip route ospf

Explanation: The show ip route ospf command filters the IPv4 routing table to display routes learned through OSPF. It is useful when an administrator needs to verify whether OSPF-learned prefixes have successfully entered the routing table. The output can provide route codes, administrative distance, metric, next-hop address, and outgoing interface. If an expected OSPF route is missing, the administrator can then investigate the OSPF database, neighbor relationships, area configuration, filtering, redistribution, and route-selection rules. This command is therefore a useful starting point for determining whether the control-plane information has resulted in an installed route.

Q100. Which routing protocol feature allows multiple EIGRP paths to be used when their metrics meet the variance requirements?

1) Summarization
2) Variance
3) Authentication
4) Passive interface

Correct Answer: 2) Variance

Explanation: EIGRP variance allows unequal-cost paths to be installed in the routing table when they meet the required feasibility and metric conditions. By default, EIGRP uses only the best successor path. With variance configured, additional feasible paths can be considered for load balancing if their metrics fall within the configured variance multiplier relative to the best route. This provides more flexibility than equal-cost load balancing because paths with different metrics can carry traffic. Administrators should ensure that candidate paths satisfy EIGRP’s feasibility requirements so that routing loops are avoided while unequal-cost load balancing is implemented correctly.