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Question 321

Which EIGRP command displays the routes and path information stored in the EIGRP topology table?

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

Correct Answer: 3

Explanation

The show ip eigrp topology command displays detailed information from the EIGRP topology table. It can show destinations, successors, feasible successors, Feasible Distance, Reported Distance, and other path information used by EIGRP’s DUAL algorithm. This makes the command useful when troubleshooting route selection and convergence. The neighbor command focuses on EIGRP adjacencies, while the interfaces command provides information about EIGRP-enabled interfaces. The routing-table command displays only routes that have been installed for forwarding. Examining the topology table is especially valuable when determining why an alternate route is not being selected or whether a feasible successor exists for a particular destination.

Question 322

Which BGP attribute is normally preferred when its value is higher and is shared with iBGP peers?

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

Correct Answer: 2

Explanation

Local Preference is normally preferred when its value is higher and is shared with internal BGP peers. It is designed to influence outbound traffic decisions within an autonomous system. For example, an organization connected to multiple external providers can assign a higher Local Preference to routes learned from a preferred provider. Because the value is propagated through iBGP, multiple internal routers can follow a consistent routing policy. Weight is also higher-is-better on Cisco routers, but it is locally significant and is not advertised to peers. MED generally favors lower values. Local Preference is therefore the common BGP attribute used for AS-wide outbound path selection.

Question 323

Which OSPF LSA type is generated by an ABR to advertise networks from one area into another?

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

Correct Answer: 3

Explanation

Type 3 Summary LSAs are generated by an OSPF Area Border Router to advertise networks from one area into another. These LSAs provide inter-area reachability information while keeping the detailed topology of each area separate. Type 1 Router LSAs describe individual routers within an area, while Type 2 Network LSAs describe multiaccess networks and are generated by DRs. Type 5 LSAs advertise external routes redistributed into OSPF. Type 3 LSAs are therefore especially important when troubleshooting inter-area routing. If an expected network from another area is missing, administrators can examine the ABR’s Type 3 LSAs and verify area connectivity and summarization policies.

Question 324

Which EIGRP packet is used to maintain neighbor relationships and discover new neighbors?

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

Correct Answer: 3

Explanation

EIGRP Hello packets are used to discover neighboring routers and maintain existing EIGRP neighbor relationships. They are sent periodically through EIGRP-enabled interfaces and contain information needed to establish and maintain adjacency. If Hellos are not received within the appropriate hold time, the router can remove the neighbor from its neighbor table. Update packets advertise routing information, Query packets request information about destinations, and Reply packets respond to Queries. When troubleshooting an EIGRP adjacency problem, administrators should verify that Hello packets can reach the neighboring router and that parameters such as autonomous system number, K-values, authentication, and interface configuration are compatible.

Question 325

Which BGP attribute is generally used to influence inbound traffic by suggesting a preferred entry point?

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

Correct Answer: 1

Explanation

MED, or Multi-Exit Discriminator, can be used to influence how another autonomous system selects an entry point when multiple connections exist between the same autonomous systems. A lower MED is generally preferred during the applicable BGP comparison. This allows an organization to suggest which link should receive inbound traffic. However, MED is only one factor in BGP path selection, and the receiving autonomous system can apply its own policies or compare MED under specific conditions. Local Preference is normally used inside an autonomous system to influence outbound traffic, while Weight is local to a Cisco router. MED is therefore commonly associated with inbound traffic engineering.

Question 326

Which OSPF state indicates that routers have established bidirectional communication but may not yet have formed a full adjacency?

1. Exchange
2. 2-Way
3. Loading
4. Full

Correct Answer: 2

Explanation

The 2-Way OSPF state indicates that bidirectional communication has been established between two routers. Each router has received a Hello containing its own Router ID from the neighbor. On broadcast and other multiaccess networks, not every OSPF router forms a Full adjacency with every other router. Routers that are not selected as DR or BDR may remain in 2-Way with one another, while full adjacencies are formed with the DR and BDR. Exchange and Loading occur later during database synchronization when a full adjacency is required. Understanding 2-Way behavior prevents administrators from incorrectly identifying a normal non-DR relationship as a failure.

Question 327

Which EIGRP route is selected as the primary path to a destination?

1. Successor
2. Feasible successor
3. Query
4. Reported Distance

Correct Answer: 1

Explanation

The EIGRP successor is the primary route selected by the router for reaching a destination. It has the lowest feasible metric among eligible EIGRP paths and is installed in the routing table. A feasible successor is an alternate loop-free path that satisfies the feasibility condition and can potentially replace the successor if the primary route fails. DUAL manages these relationships and helps maintain loop-free convergence. Reported Distance is a metric value advertised by a neighboring router rather than a route type. When troubleshooting EIGRP, identifying the successor and feasible successors in the topology table helps explain how the router will react to a topology change.

Question 328

Which BGP command provides a concise summary of BGP neighbors and their session states?

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

Correct Answer: 2

Explanation

The show ip bgp summary command provides a concise overview of BGP operation. It commonly displays the local BGP router ID, local autonomous system, configured neighbors, remote AS numbers, message counters, uptime, and the current BGP session state. It is particularly useful for quickly determining whether a neighbor is in Established state and how many prefixes have been received. The show ip bgp neighbors command provides much more detailed peer information, while show ip bgp focuses on the BGP routing table. show ip route bgp displays BGP routes installed in the IP routing table. For an initial BGP health check, the summary command is highly useful.

Question 329

Which OSPF LSA type represents a multiaccess network and is generated by the DR?

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

Correct Answer: 3

Explanation

A Type 2 Network LSA represents a multiaccess network segment and is generated by the Designated Router. It lists the routers attached to that network and helps OSPF represent the shared segment efficiently. This reduces the number of individual relationships that need to be represented in the link-state database. Type 1 LSAs are generated by individual routers, Type 3 LSAs are generated by ABRs for inter-area networks, and Type 4 LSAs identify reachability to ASBRs. Type 5 LSAs describe external routes. Type 2 LSAs are therefore closely associated with DR operation on broadcast multiaccess networks.

Question 330

Which EIGRP mechanism is responsible for maintaining loop-free paths and recalculating routes after topology changes?

1. DUAL
2. SPF
3. STP
4. TCP

Correct Answer: 1

Explanation

DUAL, or Diffusing Update Algorithm, is the EIGRP algorithm responsible for maintaining loop-free routes and calculating alternatives after topology changes. DUAL uses information such as Feasible Distance and Reported Distance to determine whether alternate paths satisfy the feasibility condition. A qualifying feasible successor can be used immediately when the current successor fails. If no feasible successor exists, EIGRP can initiate Queries to discover another path. This approach allows EIGRP to converge while maintaining loop-free routing behavior. OSPF uses SPF rather than DUAL, while STP is a Layer 2 protocol. DUAL is therefore a fundamental part of EIGRP route computation.

Question 331

Which BGP attribute identifies the IP address used as the next hop toward a destination?

1. Origin
2. Next Hop
3. MED
4. Local Preference

Correct Answer: 2

Explanation

The BGP Next Hop attribute identifies the IP address that a router should use as the next-hop destination when forwarding traffic toward a BGP route. The next-hop address must be reachable through the local routing table for the BGP route to be considered usable. In eBGP, the advertising router normally sets itself as the next hop. With iBGP, the next-hop attribute can remain unchanged unless next-hop-self or another policy modifies it. If the next hop is unreachable, a BGP route may appear in the BGP table but fail to enter the IP routing table. Next-hop reachability is therefore an important BGP troubleshooting consideration.

Question 332

Which OSPF LSA type is used for routes redistributed by an ASBR inside an NSSA?

1. Type 7
2. Type 5
3. Type 3
4. Type 4

Correct Answer: 1

Explanation

Type 7 LSAs are used to represent external routes inside an OSPF Not-So-Stubby Area. An ASBR within the NSSA can redistribute external routes and advertise them using Type 7 LSAs. An appropriate ABR can translate Type 7 LSAs into Type 5 LSAs when the routes need to be advertised outside the NSSA. This allows an NSSA to restrict external Type 5 LSAs from entering while still permitting controlled external route redistribution within the area. Type 3 LSAs handle inter-area networks, Type 4 LSAs identify ASBR reachability, and Type 5 LSAs normally represent external routes outside the NSSA context.

Question 333

Which EIGRP value represents the metric calculated by a neighbor for reaching a destination?

1. Feasible Distance
2. Reported Distance
3. Administrative Distance
4. Variance

Correct Answer: 2

Explanation

Reported Distance, also called Advertised Distance, is the metric a neighboring EIGRP router reports for reaching a destination. The local router uses this information when calculating paths and evaluating the feasibility condition. If the neighbor’s Reported Distance is lower than the local Feasible Distance, the path can qualify as a feasible successor. Feasible Distance represents the total metric calculated by the local router to reach the destination. Administrative Distance is used to compare different routing sources, while variance is a multiplier used for unequal-cost load balancing. Reported Distance is therefore an important value when analyzing EIGRP topology-table entries.

Question 334

Which BGP message is used to notify a peer about a serious protocol error?

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

Correct Answer: 3

Explanation

BGP Notification messages are used to report serious errors to a BGP peer. After sending a Notification, the router normally terminates the BGP session. Notification messages contain an error code and additional information that can help identify the reason for session termination. Open messages are used during session establishment, Keepalive messages maintain an established session, and Update messages exchange routing information. Common causes of BGP Notification messages include configuration problems, unsupported capabilities, malformed messages, or other protocol violations. When troubleshooting a BGP session that repeatedly resets, examining logs and detailed neighbor information can help identify the Notification error responsible for the termination.

Question 335

Which OSPF LSA provides information about the location of an ASBR in another area?

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

Correct Answer: 3

Explanation

A Type 4 ASBR Summary LSA provides information about how to reach an ASBR located in another OSPF area. The ABR connected to the ASBR’s area generates the Type 4 LSA and advertises reachability toward the ASBR into other areas. Type 5 LSAs contain the external routes originated by the ASBR, but routers in other areas also need a path toward the ASBR itself. Type 3 LSAs advertise inter-area networks, while Type 2 LSAs describe multiaccess networks. Understanding Type 4 and Type 5 LSAs together is important when troubleshooting external routes across multiple OSPF areas.

Question 336

Which EIGRP feature limits the routes advertised by a branch router and reduces the scope of EIGRP queries?

1. Variance
2. Stub routing
3. Split horizon
4. Delay

Correct Answer: 2

Explanation

EIGRP stub routing allows a branch router to limit the types of routes it advertises and prevents unnecessary query propagation through the branch. This is particularly useful in hub-and-spoke network designs where the branch router should not be used as a transit path. When a route becomes unavailable, limiting query propagation can improve convergence and reduce the amount of control traffic. Stub configuration can permit selected route categories such as connected, static, summary, or redistributed routes depending on the configuration. Variance handles unequal-cost load balancing, split horizon controls route advertisement direction, and delay is a metric component. Stub routing therefore provides an important scalability benefit.

Question 337

Which BGP attribute is generally preferred when its value is lower and can influence inbound path selection?

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

Correct Answer: 3

Explanation

MED is generally preferred when its value is lower during the applicable BGP best-path comparison. It can be used to influence how another autonomous system chooses among multiple entry points toward the advertising autonomous system. For example, an organization may advertise a lower MED on one external connection to suggest that it should be preferred for inbound traffic. MED does not guarantee the result because the receiving autonomous system can apply its own policies and comparison rules. Local Preference and Weight are normally higher-is-better attributes, while Origin represents how a route entered BGP. MED is therefore commonly associated with lower-value path preference.

Question 338

Which OSPF command is commonly used to display the router ID and general OSPF process information?

1. show ip ospf
2. show ip ospf neighbor
3. show ip route ospf
4. show ip ospf database

Correct Answer: 1

Explanation

The show ip ospf command provides general information about the local OSPF process. Depending on the platform and configuration, its output can include the OSPF process ID, router ID, area information, SPF statistics, timers, and other operational details. This makes it useful for verifying basic OSPF process configuration. The show ip ospf neighbor command focuses on neighbor relationships, show ip ospf database displays LSDB contents, and show ip route ospf displays OSPF routes installed in the routing table. When initially troubleshooting an OSPF process, verifying the router ID, areas, and process information is an important first step.

Question 339

Which EIGRP route can be installed immediately if the current successor fails and the route satisfies the feasibility condition?

1. External route
2. Feasible successor
3. Query route
4. Summary-only route

Correct Answer: 2

Explanation

A feasible successor is an alternate EIGRP route that satisfies the feasibility condition and can be used when the current successor becomes unavailable. Because DUAL has already determined that the alternate path is loop-free, the router can often install the feasible successor without first sending Queries throughout the network. This provides fast convergence. The feasibility condition requires the neighbor’s Reported Distance to be less than the local Feasible Distance. If no feasible successor exists, EIGRP may need to enter an active state and query neighbors for an alternative route. Feasible successors are therefore important for rapid EIGRP convergence.

Question 340

Which BGP attribute is evaluated after Weight and Local Preference and generally favors routes with a shorter AS Path?

1. Origin
2. MED
3. AS Path
4. Next Hop

Correct Answer: 3

Explanation

AS Path is an important BGP path-selection attribute evaluated after earlier attributes such as Weight and Local Preference in Cisco’s best-path process. When comparing otherwise suitable routes, BGP generally prefers the route with the shorter AS Path. The AS Path also serves as a loop-prevention mechanism because a router normally rejects a route if its own AS number appears in the received path. Origin and MED are evaluated later, while Next Hop identifies the forwarding destination rather than directly representing path length. Understanding AS Path is therefore important for both BGP loop prevention and route-selection troubleshooting.