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Q341. Which OSPF LSA type is generated by an ABR to advertise networks from one area into another area?
1) Type 1
2) Type 2
3) Type 3
4) Type 5
Correct Answer: 3) Type 3
Explanation:
OSPF Type 3 LSAs, also called Summary LSAs, are generated by Area Border Routers (ABRs) to advertise networks learned from one OSPF area into another area. They allow routers in different areas to learn about inter-area destinations while maintaining the hierarchical OSPF structure. Type 1 LSAs describe router information within an area, while Type 2 LSAs describe transit network information generated by a DR. Type 5 LSAs are used for external routes redistributed into OSPF. Understanding Type 3 LSAs is important when troubleshooting inter-area connectivity, route summarization, and unexpected OSPF routes between different areas.
Q342. Which OSPF area type allows external routes to be introduced using Type 7 LSAs?
1) Stub area
2) NSSA
3) Backbone area
4) Totally stubby area
Correct Answer: 2) NSSA
Explanation:
A Not-So-Stubby Area, or NSSA, allows external routes to be redistributed into the area while still limiting the normal external LSAs entering from outside. Routes redistributed inside an NSSA are represented using Type 7 LSAs. An NSSA router or ABR can translate appropriate Type 7 LSAs into Type 5 LSAs when those routes need to be advertised into the rest of the OSPF domain. This design is useful when an area needs limited external connectivity but administrators still want the area to retain some stub-like characteristics. NSSA configuration must be carefully planned because Type 7 translation and default-route behavior can affect routing decisions.
Q343. What is the main purpose of an OSPF virtual link?
1) To connect two non-adjacent physical interfaces
2) To logically connect an area to the OSPF backbone
3) To replace all OSPF authentication
4) To create an MPLS tunnel
Correct Answer: 2) To logically connect an area to the OSPF backbone
Explanation:
An OSPF virtual link provides a logical connection through a transit area so that an OSPF area can maintain connectivity to Area 0 when a direct physical connection to the backbone is not possible. OSPF requires every non-backbone area to have a logical connection to Area 0. A virtual link uses the underlying OSPF path through a transit area to establish the required logical adjacency. It should generally be considered a temporary or special-purpose design rather than the preferred long-term topology. Administrators should verify the transit area’s stability, area configuration, and router IDs when troubleshooting virtual-link problems.
Q344. Which EIGRP command displays successor and feasible successor information for routes?
1) show ip eigrp topology
2) show ip ospf database
3) show ip bgp neighbors
4) show ip nhrp
Correct Answer: 1) show ip eigrp topology
Explanation:
The show ip eigrp topology command provides detailed information about routes in the EIGRP topology table. It can display the successor, feasible distance, reported distance, and information about feasible successors when available. This makes the command especially useful when troubleshooting EIGRP path selection and convergence. The routing table shows the routes that are currently installed for forwarding, but the topology table contains additional information about paths that EIGRP knows about but may not currently be using. Administrators can therefore use the topology command to determine why an alternate route is or is not considered a feasible successor.
Q345. Which EIGRP packet type is used to discover and maintain neighbor relationships?
1) Update
2) Query
3) Hello
4) Reply
Correct Answer: 3) Hello
Explanation:
EIGRP Hello packets are used to discover and maintain neighboring EIGRP routers. When routers receive valid Hello messages from one another, they can establish and maintain neighbor relationships if other required parameters match. Hello packets do not normally carry complete routing updates; instead, they serve as a mechanism for neighbor discovery and keepalive communication. EIGRP also uses Update packets to advertise routing information, Query packets when searching for alternate paths, and Reply packets in response to queries. When troubleshooting an EIGRP adjacency, administrators should check interface connectivity, AS number, authentication, K values, network configuration, and whether Hello packets are being exchanged.
Q346. Which BGP attribute is normally preferred when its value is higher and is propagated throughout an autonomous system?
1) MED
2) Local Preference
3) AS_PATH length
4) Origin
Correct Answer: 2) Local Preference
Explanation:
BGP Local Preference is used within an autonomous system to influence which exit point should be preferred for outbound traffic. When comparing otherwise suitable routes, a higher Local Preference is preferred. Unlike the Cisco-specific Weight attribute, Local Preference is carried to other BGP routers within the same autonomous system, making it appropriate for establishing consistent outbound routing policies across multiple routers. Administrators often modify Local Preference using route maps, prefix lists, or other policy tools. A higher value can make one ISP connection more attractive than another. This provides a scalable way to control outbound traffic without changing the physical topology.
Q347. What is the primary purpose of a BGP community attribute?
1) To identify and group routes for routing-policy purposes
2) To replace the AS_PATH
3) To provide packet encryption
4) To calculate OSPF cost
Correct Answer: 1) To identify and group routes for routing-policy purposes
Explanation:
BGP communities provide a flexible way to tag and group routes so that routing policies can be applied consistently. Instead of creating a separate policy for every individual prefix, administrators can assign a community to a group of routes and then use that community as a matching condition in route policies. Communities can be standard, extended, or large, depending on the design and implementation. Well-known communities such as no-export can also influence how routes are propagated. Communities do not directly determine the BGP best path by themselves; rather, they provide policy information that can be used to modify attributes, filter routes, or control advertisement behavior.
Q348. Which BGP well-known community prevents a route from being advertised outside the local autonomous system?
1) internet
2) no-export
3) local-AS
4) accept-own
Correct Answer: 2) no-export
Explanation:
The BGP no-export community tells a BGP router that a route should not be advertised to external BGP peers outside the local autonomous system. This community is useful when a route should be shared among routers within an organization but should not be propagated to other autonomous systems. It can help implement controlled route distribution and reduce unnecessary route advertisements. The community must be properly recognized and preserved by the relevant BGP policy configuration. Administrators should also understand the distinction between no-export, which restricts external propagation, and other communities such as no-advertise, which can prevent a route from being advertised to any BGP peer.
Q349. Which command can be used to view the BGP routes installed in the routing table for a specific network?
1) show ip bgp <network>
2) show ip ospf <network>
3) show ip eigrp route <network>
4) show mpls route <network>
Correct Answer: 1) show ip bgp <network>
Explanation:
The show ip bgp <network> command can be used to examine BGP information for a particular network prefix. It provides details about available BGP paths, including attributes and the selected best path. This is useful when a route is present in BGP but does not appear in the IP routing table, because administrators can inspect the competing paths and determine whether another route was selected or whether a next-hop problem exists. Additional commands such as show ip route and show ip bgp neighbors can complement the investigation. Effective BGP troubleshooting requires checking both the BGP table and the main routing table.
Q350. Which BGP attribute is commonly manipulated to make a route appear longer and therefore less preferred to an external neighbor?
1) Weight
2) Local Preference
3) AS_PATH
4) Router ID
Correct Answer: 3) AS_PATH
Explanation:
AS-path prepending adds additional instances of the local autonomous system number to the AS_PATH attribute. This makes the path appear longer to external BGP neighbors, which generally causes that path to become less attractive when compared with an otherwise similar shorter path. Network administrators commonly use this technique to influence inbound traffic by making one Internet connection less preferred than another. AS-path prepending does not physically change the route’s destination or make the link unavailable; it simply influences BGP’s path-selection process. Because inbound traffic is controlled by remote networks, prepending is a policy mechanism rather than a guaranteed method of controlling every incoming flow.
Q351. Which MPLS component is normally responsible for assigning VPN labels to customer routes?
1) Provider router in the core
2) Provider Edge router
3) Customer access switch
4) Internet firewall
Correct Answer: 2) Provider Edge router
Explanation:
In an MPLS Layer 3 VPN architecture, Provider Edge (PE) routers maintain customer VRFs and participate in MP-BGP to exchange VPNv4 or VPNv6 routing information. The PE routers are responsible for associating customer routes with VPN forwarding information and distributing the appropriate VPN labels. Core Provider (P) routers do not need to maintain customer-specific VPN routing tables; they primarily forward MPLS packets based on transport labels. This separation is one of the major scalability benefits of MPLS L3VPNs. When troubleshooting VPN forwarding, administrators should therefore examine the PE’s VRF, MP-BGP routes, label bindings, and MPLS forwarding entries.
Q352. What is the purpose of the MPLS label distribution protocol LDP?
1) To assign IP addresses to customer devices
2) To distribute label bindings for routes
3) To encrypt MPLS packets
4) To replace BGP completely
Correct Answer: 2) To distribute label bindings for routes
Explanation:
Label Distribution Protocol, or LDP, is used by MPLS routers to exchange label bindings associated with network prefixes. These bindings allow routers to construct label-switched paths based on the underlying IP routing information. LDP neighbors establish sessions and exchange information that tells routers which labels should be used for particular forwarding entries. LDP does not encrypt traffic and does not replace BGP in MPLS Layer 3 VPN architectures. Instead, BGP can distribute VPN-specific routing information while LDP provides transport labels across the provider core. When troubleshooting MPLS, administrators often inspect both the IP routing table and LDP neighbor and label information.
Q353. Which command is useful for verifying LDP neighbor relationships?
1) show mpls ldp neighbor
2) show ip nhrp
3) show crypto isakmp sa
4) show standby brief
Correct Answer: 1) show mpls ldp neighbor
Explanation:
The show mpls ldp neighbor command is useful for verifying LDP neighbor relationships between MPLS-enabled routers. It provides information about established LDP sessions and helps administrators determine whether neighboring routers are successfully exchanging label-distribution information. If an expected LDP neighbor is missing, troubleshooting should include checking MPLS configuration, interface activation, IP connectivity, router IDs, transport addresses, and any relevant access-control policies. LDP must operate correctly before expected label bindings can be exchanged. This command should therefore be part of the standard troubleshooting process when MPLS forwarding appears incomplete or when an MPLS label-switched path is not functioning as expected.
Q354. Which DMVPN command provides a summary of tunnel peers and their NHRP-related state?
1) show dmvpn
2) show ip ospf neighbor
3) show ip bgp summary
4) show crypto map
Correct Answer: 1) show dmvpn
Explanation:
The show dmvpn command provides a convenient summary of DMVPN tunnel peers and related information. It can help administrators identify whether spokes have established dynamic relationships, whether tunnel endpoints are known, and whether the expected DMVPN topology is present. This command is especially useful when troubleshooting NHRP registration and spoke-to-spoke communication. Additional commands such as show ip nhrp provide more detailed NHRP mappings, while show crypto ipsec sa can be used to inspect IPsec protection. Effective DMVPN troubleshooting typically examines the tunnel interface, NHRP state, routing information, and IPsec security associations together.
Q355. Which QoS mechanism reserves 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, or LLQ, provides a strict priority queue for delay-sensitive traffic. It is commonly used for voice and other traffic that is highly sensitive to delay and jitter. LLQ is implemented as an extension of Class-Based Weighted Fair Queuing and allows selected traffic classes to receive priority service during congestion. However, administrators must configure the priority queue carefully because excessive priority traffic can potentially starve other classes. QoS design should therefore include appropriate bandwidth limits and classification rules. LLQ does not automatically identify voice traffic; administrators must define which traffic belongs to the priority class through appropriate classification and policy configuration.
Q356. Which QoS mechanism temporarily buffers traffic and sends it at a controlled rate to smooth bursts?
1) Policing
2) Shaping
3) Marking
4) Classification
Correct Answer: 2) Shaping
Explanation:
Traffic shaping controls the rate at which packets are transmitted by buffering excess traffic and releasing it at a configured rate. This makes shaping particularly useful when an interface or service provider expects traffic to conform to a specific rate. Because shaping can buffer packets, it can smooth traffic bursts rather than immediately discarding packets that exceed the configured rate. Policing works differently because it typically evaluates traffic against a rate and may drop or remark packets that exceed the configured policy. Understanding this difference is important when designing WAN QoS policies. Shaping is often used on egress interfaces where traffic must conform to a provider’s contracted bandwidth.
Q357. Which command can be used to verify IP SLA operation results and statistics?
1) show ip sla statistics
2) show ip ospf interface
3) show ip bgp community
4) show mpls ldp discovery
Correct Answer: 1) show ip sla statistics
Explanation:
The show ip sla statistics command displays operational statistics for configured IP SLA measurements. It can help administrators determine whether a probe is succeeding and provide information about response times, failures, and other measurement results depending on the configured operation. IP SLA can monitor services such as ICMP reachability, HTTP response, DNS performance, or other supported operations. These measurements can be combined with object tracking to trigger changes in routing or first-hop redundancy behavior. When troubleshooting an IP SLA-based failover design, administrators should verify the operation configuration, schedule status, statistics, tracked-object state, and the resulting routing or HSRP behavior.
Q358. Which HSRP protocol version supports IPv6 address families?
1) HSRP version 1 only
2) HSRP version 2
3) HSRP version 0
4) HSRP version 1 with IPv4 NAT
Correct Answer: 2) HSRP version 2
Explanation:
HSRP version 2 provides improvements over HSRP version 1 and supports IPv6 first-hop redundancy. IPv6 networks require first-hop redundancy mechanisms that can operate with IPv6 addressing, and HSRPv2 provides the necessary capabilities. HSRPv2 also changes the multicast address used by HSRP and supports a larger group-number range than version 1. When implementing HSRP for IPv6, administrators should ensure that the participating routers use compatible configuration and that the appropriate IPv6 addressing and HSRP parameters are present. HSRP provides gateway redundancy, allowing hosts to continue using a virtual default gateway when the currently active router becomes unavailable.
Q359. Which IPv6 protocol is responsible for resolving a neighbor’s link-layer address?
1) ARP
2) NDP
3) DHCP
4) BGP
Correct Answer: 2) NDP
Explanation:
IPv6 uses Neighbor Discovery Protocol, or NDP, instead of ARP to discover the link-layer address associated with an IPv6 neighbor. NDP operates through ICMPv6 messages, particularly Neighbor Solicitation and Neighbor Advertisement messages. A host can send a Neighbor Solicitation to determine the MAC address associated with another IPv6 address on the local network, and the destination can respond with a Neighbor Advertisement. NDP also provides functions related to router discovery, address resolution, duplicate address detection, and neighbor reachability. Understanding NDP is essential when troubleshooting IPv6 LAN communication because traditional IPv4 ARP troubleshooting techniques do not directly apply.
Q360. Which command provides a general overview of the routing protocols and networks configured on a Cisco router?
1) show ip protocols
2) show interfaces counters
3) show arp
4) show version
Correct Answer: 1) show ip protocols
Explanation:
The show ip protocols command provides a useful overview of the IP routing protocols configured on a Cisco router. Depending on the protocols in use, the output can include information about routing processes, configured networks, passive interfaces, redistribution, filtering, timers, and other routing-related settings. This makes it valuable during initial troubleshooting because administrators can quickly verify whether the expected routing protocol is enabled and whether the correct networks are participating. It does not replace protocol-specific commands such as show ip ospf or show ip eigrp topology, but it provides a high-level view that can reveal configuration problems before more detailed investigation is performed.