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Question 101

Which EIGRP command displays the EIGRP neighbors discovered by a router?

1. show ip eigrp topology
2. show ip eigrp interfaces
3. show ip eigrp neighbors
4. show ip route eigrp

Correct Answer: 3

Explanation

The show ip eigrp neighbors command displays the EIGRP neighbor table. It provides information about routers with which the local router has established EIGRP adjacencies. The output commonly includes the neighbor’s IP address, hold time, interface, uptime, sequence number, and queue information. This command is useful when troubleshooting EIGRP adjacency problems because it confirms whether expected neighbors have been discovered and maintained. The topology command provides route information, while show ip eigrp interfaces displays interface-specific EIGRP information. If a neighbor is missing from the neighbor table, administrators should investigate connectivity, AS numbers, K-values, authentication, passive interfaces, and other EIGRP configuration parameters.

Question 102

Which BGP attribute is propagated to internal BGP peers and normally used to control outbound traffic?

1. MED
2. Local Preference
3. Weight
4. Origin

Correct Answer: 2

Explanation

Local Preference is a BGP attribute used within an autonomous system to influence outbound traffic decisions. It is normally advertised to internal BGP peers and is not sent to external BGP peers in the same manner. A higher Local Preference value is generally preferred during BGP best-path selection. Organizations can use this attribute to designate a preferred exit point when multiple external connections are available. For example, an enterprise connected to two Internet service providers can assign a higher Local Preference to routes learned through its preferred provider. Unlike Weight, which is Cisco-specific and local to one router, Local Preference can influence path selection across multiple routers in the autonomous system.

Question 103

Which OSPF LSA type describes the links and networks within a single OSPF router’s area?

1. Type 1
2. Type 3
3. Type 4
4. Type 5

Correct Answer: 1

Explanation

A Type 1 LSA, also called a Router LSA, is generated by every OSPF router and describes the router’s links, interfaces, neighbors, and associated costs within an area. Type 1 LSAs remain within the originating OSPF area and form an important part of the link-state database used by the SPF algorithm. Type 2 LSAs are generated by the DR on multiaccess networks, while Type 3 LSAs are generated by ABRs to advertise networks between areas. Type 4 and Type 5 LSAs are associated with ASBR reachability and external routes. Understanding Type 1 LSAs is essential when analyzing OSPF topology databases.

Question 104

Which EIGRP packet is sent when a router needs information about a route that has become unreachable and no feasible successor is available?

1. Reply
2. Update
3. Query
4. Hello

Correct Answer: 3

Explanation

An EIGRP Query packet is sent when a router loses its successor and does not have a feasible successor available for the affected destination. The router must then determine whether another path exists through its neighbors. It sends Query messages requesting information about alternative routes. Neighboring routers respond with Reply packets indicating whether they have a valid path. This process is part of EIGRP’s DUAL algorithm and helps maintain loop-free routing during convergence. Excessive Query propagation can create scalability and convergence problems, which is one reason EIGRP stub configurations and appropriate network design are useful in larger environments.

Question 105

Which BGP message is exchanged periodically to maintain an established BGP session?

1. Update
2. Keepalive
3. Notification
4. Open

Correct Answer: 2

Explanation

BGP Keepalive messages are exchanged periodically between BGP peers to confirm that the session remains operational. BGP runs over TCP, but the Keepalive mechanism provides BGP-specific session maintenance. If a router does not receive expected messages within the configured hold time, it can consider the peer unavailable and terminate the BGP session. Open messages are used when establishing a BGP session, while Update messages carry routing information. Notification messages indicate serious protocol errors and normally terminate the session. Keepalive messages therefore play an important role in detecting failed or unreachable BGP peers and maintaining stable BGP adjacencies.

Question 106

Which OSPF area type replaces external Type 5 LSAs with a default route?

1. Stub area
2. NSSA
3. Totally NSSA
4. Backbone area

Correct Answer: 1

Explanation

A standard OSPF stub area blocks external Type 5 LSAs from entering the area and uses a default route to provide reachability toward destinations outside the area. This reduces the amount of external routing information that routers inside the stub area must process. The ABR typically advertises the default route into the stub area. An NSSA provides a different capability because it allows limited external route redistribution through Type 7 LSAs. Totally stubby areas further restrict inter-area information by suppressing Type 3 and Type 4 LSAs while providing a default route. Choosing the appropriate area type depends on the desired routing information and redistribution requirements.

Question 107

Which EIGRP command can be used to display detailed information about EIGRP-enabled interfaces?

1. show ip eigrp interfaces
2. show ip eigrp neighbors
3. show ip eigrp topology
4. show ip route

Correct Answer: 1

Explanation

The show ip eigrp interfaces command displays information about interfaces participating in EIGRP. Depending on the platform and command options, the output can include the interface, EIGRP process, peers, packet information, authentication status, and other interface-specific details. This makes the command useful for troubleshooting whether EIGRP is correctly operating on a particular interface. The neighbor command focuses on adjacency information, while the topology command focuses on routes and path information. When an expected EIGRP neighbor does not appear, checking the interface configuration, network statements, passive-interface settings, and EIGRP parameters can help identify the cause.

Question 108

Which BGP attribute is normally preferred when it has a lower value?

1. Local Preference
2. Weight
3. MED
4. AS Path

Correct Answer: 3

Explanation

The Multi-Exit Discriminator, or MED, is normally preferred when it has a lower value during the relevant stage of BGP best-path selection. MED can be used to suggest which entry point into an autonomous system should be preferred when multiple links exist between autonomous systems. For example, an organization may advertise a lower MED on one connection to encourage inbound traffic through that link. MED is not universally decisive because BGP policy and other path attributes may take precedence. By comparison, Local Preference and Weight generally favor higher values. AS Path is generally preferred when shorter, subject to the specific BGP decision process and configuration.

Question 109

Which OSPF packet is responsible for requesting specific LSAs that are missing or outdated?

1. Link-State Update
2. Database Description
3. Link-State Request
4. Link-State Acknowledgment

Correct Answer: 3

Explanation

The OSPF Link-State Request packet is used when a router needs specific LSAs from a neighbor. During database synchronization, routers compare the information contained in their Database Description packets. If one router determines that it has a missing or older LSA, it sends a Link-State Request asking the neighbor to provide the required information. The neighbor responds with a Link-State Update containing the requested LSAs. Link-State Acknowledgment packets confirm receipt of LSAs, while Database Description packets summarize the database during adjacency formation. Understanding this packet sequence is useful when troubleshooting OSPF neighbors that become stuck during database synchronization.

Question 110

Which EIGRP route summarization feature can reduce the size of routing tables and limit query propagation?

1. Automatic summarization only
2. Manual route summarization
3. Split horizon
4. Variance

Correct Answer: 2

Explanation

Manual EIGRP route summarization allows an administrator to advertise multiple more-specific routes as a single summary prefix. This can reduce routing table size and simplify the routing information exchanged between routers. Summarization can also provide a boundary that helps limit EIGRP query propagation because routers receiving the summary do not need to know every individual subnet behind it. On modern Cisco networks, manual summarization is generally preferred because it provides precise control over where summaries are advertised. Automatic summarization was used in older EIGRP configurations but is typically disabled in modern designs to avoid unexpected routing behavior across discontiguous networks.

Question 111

Which BGP attribute is Cisco-specific and is not advertised to BGP peers?

1. Weight
2. Local Preference
3. MED
4. AS Path

Correct Answer: 1

Explanation

Weight is a Cisco-specific BGP attribute used locally on a router to influence the selection of a best path. Unlike attributes such as Local Preference, AS Path, and MED, Weight is not propagated to BGP neighbors. A higher Weight is preferred by the local Cisco router. This makes Weight useful when an administrator wants to influence path selection on one specific router without changing the routing policy of other routers in the autonomous system. Because it is local, applying a Weight value on one router does not automatically affect other BGP routers. This distinction is important when troubleshooting inconsistent BGP path selections across multiple routers.

Question 112

Which OSPF router type connects an OSPF area to the backbone area?

1. ASBR
2. Internal router
3. ABR
4. DR

Correct Answer: 3

Explanation

An Area Border Router, or ABR, connects one or more non-backbone OSPF areas to the OSPF backbone, Area 0. An ABR maintains separate link-state databases for the areas to which it is connected and performs inter-area route exchange. It can generate Type 3 Summary LSAs to advertise networks from one area into another. An ASBR, in contrast, connects OSPF to an external routing domain and redistributes external routes into OSPF. A DR is elected on certain multiaccess networks and does not define an area boundary. Understanding the ABR role is fundamental to designing and troubleshooting multi-area OSPF networks.

Question 113

Which EIGRP packet is used to advertise routing information reliably to neighbors?

1. Update
2. Hello
3. Acknowledgment
4. Reply

Correct Answer: 1

Explanation

EIGRP Update packets carry routing information to neighboring EIGRP routers. Updates can advertise new routes, changes to existing routes, or route withdrawals. EIGRP uses reliable delivery for important routing information, so Update packets are acknowledged when appropriate. Hello packets are primarily used for neighbor discovery and maintaining adjacency, while Query and Reply packets support the DUAL convergence process. EIGRP’s partial and bounded update behavior allows routers to send only relevant changes instead of periodically sending the entire routing table. This helps reduce unnecessary bandwidth consumption and allows EIGRP to converge efficiently when network topology changes.

Question 114

Which BGP attribute contains the list of autonomous systems through which a route has passed?

1. Origin
2. MED
3. Local Preference
4. AS Path

Correct Answer: 4

Explanation

The AS Path attribute contains a sequence of autonomous system numbers through which a BGP route has passed. Each eBGP autonomous system normally adds its own AS number when advertising a route to another autonomous system. The AS Path serves several purposes, including loop prevention and influencing path selection. A route containing the local autonomous system number is normally rejected because it indicates a potential routing loop. AS-path prepending can also be used to artificially lengthen the path to influence inbound traffic decisions. Because AS Path is carried with BGP route advertisements, it provides important information about the external path associated with each route.

Question 115

Which OSPF LSA is generated by a Designated Router on a broadcast multiaccess network?

1. Type 1
2. Type 2
3. Type 3
4. Type 5

Correct Answer: 2

Explanation

A Type 2 LSA, known as a Network LSA, is generated by the Designated Router on a multiaccess OSPF network such as Ethernet. It represents the shared network segment and identifies the routers connected to that segment. The use of a Type 2 LSA helps OSPF model a multiaccess network efficiently rather than requiring every router on the segment to form a full adjacency with every other router. Type 1 LSAs describe individual routers, while Type 3 LSAs are generated by ABRs for inter-area network advertisements. If no DR is required, such as on a point-to-point network, a Type 2 LSA is not generated for that segment.

Question 116

Which EIGRP feature prevents routing loops by ensuring that a backup route satisfies the feasibility condition?

1. Query process
2. Split horizon
3. Feasible successor
4. Route filtering

Correct Answer: 3

Explanation

An EIGRP feasible successor is an alternate route that satisfies the feasibility condition and is therefore considered loop-free. The neighboring router’s reported distance must be lower than the current feasible distance for the destination. Because the route has already been verified as loop-free, EIGRP can use it immediately if the current successor fails. This can significantly reduce convergence time because the router does not need to initiate a full query process for that destination. If no feasible successor exists, EIGRP may need to query neighboring routers and perform additional DUAL calculations. Feasible successors are therefore an important part of EIGRP fast convergence.

Question 117

Which BGP command displays detailed information about a specific BGP neighbor?

1. show ip bgp summary
2. show ip bgp neighbors
3. show ip route bgp
4. show ip protocols

Correct Answer: 2

Explanation

The show ip bgp neighbors command displays detailed information about BGP peer relationships. The output can include the neighbor’s remote autonomous system, BGP state, timers, message counters, capabilities, route policies, prefixes received and advertised, and other session details. It is especially useful when troubleshooting a BGP session that is not reaching the Established state or when investigating why particular routes are being accepted or advertised. The summary command provides a shorter overview of all peers, while show ip route bgp focuses on BGP routes installed in the routing table. Detailed neighbor output can reveal configuration and session-level information that the summary does not show.

Question 118

Which OSPF area is required to connect all other OSPF areas in a standard multi-area design?

1. Area 1
2. Area 10
3. Area 100
4. Area 0

Correct Answer: 4

Explanation

Area 0, also called the backbone area, is the central area used to connect other OSPF areas in a standard multi-area OSPF design. Inter-area routing normally occurs through the backbone, and ABRs connect non-backbone areas to Area 0. This hierarchical structure improves scalability by limiting detailed link-state information within individual areas. While OSPF can support virtual links for certain topology situations, a properly designed network generally maintains physical or logical connectivity between ABRs and the backbone. Area 1, Area 10, and Area 100 can all be valid non-backbone area numbers, but they do not replace the role of Area 0 in standard OSPF architecture.

Question 119

Which EIGRP administrative distance is assigned to an internal EIGRP route by default?

1. 90
2. 100
3. 110
4. 170

Correct Answer: 1

Explanation

Cisco routers assign an administrative distance of 90 to internal EIGRP routes by default. Administrative distance is used to compare the trustworthiness of routes learned from different routing sources. A lower administrative distance is preferred when multiple routing protocols provide routes to the same destination. External EIGRP routes have a default administrative distance of 170 because they were learned through redistribution or another external source. OSPF has a default administrative distance of 110, while eBGP commonly uses 20. Understanding these values is important when multiple routing protocols operate simultaneously and a router must determine which routing source should be installed.

Question 120

Which BGP attribute is primarily used to prevent routing loops between autonomous systems?

1. Weight
2. AS Path
3. MED
4. Local Preference

Correct Answer: 2

Explanation

The AS Path attribute is one of the primary mechanisms BGP uses to prevent routing loops between autonomous systems. When an eBGP router advertises a route to another autonomous system, its own AS number is normally added to the AS Path. If a BGP router receives a route containing its own autonomous system number, it can reject that route because the advertisement has already passed through the same AS. This provides an important loop-prevention mechanism for inter-domain routing. AS Path also participates in BGP best-path selection, where a shorter path is generally preferred over a longer path when higher-priority attributes do not determine the result.