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Question 161

Which EIGRP command displays all feasible paths for destinations, including paths that are not currently installed in the routing table?

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

Correct Answer: 2

Explanation

The show ip eigrp topology command displays information from the EIGRP topology table, including known routes, feasible distances, reported distances, successors, and qualifying alternate paths. This makes it useful for examining paths that are not currently installed in the IP routing table. The routing table normally contains only the routes selected for forwarding, while the topology table maintains additional EIGRP path information. Administrators can use this command to determine whether an alternate path satisfies the feasibility condition and can act as a feasible successor. It is particularly valuable when troubleshooting EIGRP convergence, path selection, and unexpected routing behavior.

Question 162

Which BGP attribute is normally preferred when it has the highest value?

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

Correct Answer: 2

Explanation

Local Preference is generally preferred when it has a higher value. It is used within an autonomous system to influence which external exit point should be selected for outbound traffic. Because Local Preference is propagated through internal BGP, administrators can establish consistent outbound routing policies across multiple routers. For example, an organization may assign a Local Preference of 200 to routes learned from a preferred provider and 100 to routes from a secondary provider. The higher value is normally selected when the BGP decision process reaches this attribute. Cisco’s Weight attribute is considered before Local Preference and can override the decision locally when configured.

Question 163

Which OSPF command displays the current OSPF neighbor adjacencies and their states?

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

Correct Answer: 1

Explanation

The show ip ospf neighbor command displays OSPF neighbor relationships and their current states. The output commonly includes the neighbor router ID, priority, state, dead timer, address, and local interface. It is one of the primary commands used to troubleshoot OSPF adjacency problems. States such as Init, 2-Way, ExStart, Exchange, Loading, and Full indicate different stages of the adjacency process. On broadcast networks, not every router necessarily reaches Full state with every other router because the DR and BDR reduce the number of required adjacencies. Checking this command can quickly identify whether expected OSPF neighbors are established correctly.

Question 164

Which EIGRP metric parameter is normally calculated using the minimum bandwidth along the complete route?

1. Delay
2. Reliability
3. Bandwidth
4. Load

Correct Answer: 3

Explanation

EIGRP uses the minimum bandwidth along the complete path as part of its composite metric calculation. It does not add the bandwidth values of all interfaces. Instead, the lowest bandwidth value becomes the bandwidth component used in the calculation. Delay is handled differently because EIGRP accumulates delay across all interfaces in the path. By default, bandwidth and delay are the primary active metric components. Reliability and load can be included when the corresponding K-values are changed, although modifying K-values is uncommon in production networks. Understanding how bandwidth contributes to the EIGRP metric helps explain why a path containing one slow interface may be less preferred than another route.

Question 165

Which BGP attribute is commonly used to make a particular route less attractive for inbound traffic by increasing its AS Path length?

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

Correct Answer: 3

Explanation

AS-path prepending can be used to make a BGP route appear to have a longer AS Path. An organization can add its own autonomous system number multiple times when advertising a route to an external neighbor. Other networks may then consider the path less attractive when comparing routes and may select another available path if other attributes do not take precedence. This technique is generally used to influence inbound traffic. However, BGP policies are controlled independently by each autonomous system, so AS-path prepending does not guarantee a particular inbound path. It is therefore best understood as a routing-policy mechanism rather than a strict traffic-engineering command.

Question 166

Which OSPF state indicates that routers are exchanging Database Description packets?

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

Correct Answer: 2

Explanation

The OSPF Exchange state is the stage in which neighboring routers exchange Database Description packets. These packets contain summaries of the LSAs contained in each router’s link-state database. The routers compare the received information with their own databases and identify LSAs that are missing or outdated. They can then use Link-State Request packets to request additional information and Link-State Update packets to receive the required LSAs. After synchronization is complete, the adjacency normally progresses toward the Full state. If an OSPF neighbor becomes stuck in Exchange, administrators should investigate issues such as MTU mismatches, packet loss, network type inconsistencies, or other configuration problems.

Question 167

Which EIGRP route type is learned from another routing protocol through redistribution?

1. Internal route
2. External route
3. Connected route
4. Summary-only route

Correct Answer: 2

Explanation

An EIGRP external route is a route that enters EIGRP through redistribution from another routing source. Examples include routes redistributed from OSPF, BGP, RIP, static routing, or another protocol. External EIGRP routes have a default administrative distance of 170, compared with 90 for internal EIGRP routes. The EIGRP topology information identifies external routes with additional information about their original source and redistribution details. Understanding the difference between internal and external EIGRP routes is especially important in networks using multiple routing protocols. Redistribution should be carefully designed because it can introduce routing loops, unexpected path selection, and additional routing complexity.

Question 168

Which BGP message carries network reachability information and path attributes?

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

Correct Answer: 2

Explanation

BGP Update messages carry routing information between BGP peers. An Update can advertise reachable prefixes and include associated path attributes such as AS Path, Origin, Next Hop, MED, and Local Preference where applicable. Updates can also withdraw routes that are no longer reachable. Unlike traditional distance-vector protocols that periodically exchange complete routing tables, BGP generally sends incremental updates when routing information changes. This helps reduce unnecessary routing traffic. Open messages establish the BGP session, Keepalive messages maintain the session, and Notification messages report serious errors. Understanding Update messages is essential when troubleshooting route advertisements, withdrawals, and BGP policy behavior.

Question 169

Which OSPF LSA type is generated by a router to describe its own links within an area?

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

Correct Answer: 1

Explanation

Type 1 OSPF LSAs are Router LSAs generated by every OSPF router for each area in which it participates. They describe the router’s links, connected networks, neighbors, and associated OSPF costs within that area. These LSAs remain within the originating area and contribute to the link-state database used by the SPF algorithm. A Type 2 LSA represents a multiaccess network and is generated by the DR. Type 3 LSAs advertise inter-area networks, while Type 4 LSAs identify the location of an ASBR. Examining Type 1 LSAs can help administrators understand the topology information OSPF uses to calculate routes within an area.

Question 170

Which EIGRP feature allows a router to advertise a limited set of routes to a neighboring router and reduce query propagation?

1. Variance
2. Stub routing
3. Split horizon
4. Feasibility condition

Correct Answer: 2

Explanation

EIGRP stub routing allows a router to identify itself as a stub and advertise only selected types of routing information to its neighbor. This is commonly used for branch or spoke routers that should not be treated as transit routers. By limiting what the stub router can advertise and reducing the destinations for which it may need to respond to Queries, EIGRP stub routing helps control Query propagation. This improves scalability and can reduce convergence overhead in hub-and-spoke environments. Stub routing does not replace the EIGRP feasibility condition or variance. Instead, it provides a topology-control mechanism that helps define the role and routing behavior of specific EIGRP neighbors.

Question 171

Which BGP attribute is used to identify the IP address that should be used as the next hop for a BGP route?

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

Correct Answer: 3

Explanation

The BGP Next Hop attribute identifies the IP address that a router should use as the next hop toward a particular BGP destination. Proper reachability to the next-hop address is necessary for the BGP route to be usable. In eBGP, the advertising router normally sets itself as the next hop. In iBGP, the next-hop attribute can remain unchanged when a route is passed internally, which can cause reachability issues if internal routers do not have a route to the original next hop. The next-hop-self feature can be configured on an iBGP router when appropriate. Checking next-hop reachability is therefore an important part of BGP troubleshooting.

Question 172

Which OSPF network type is commonly used on Ethernet and supports DR and BDR elections?

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

Correct Answer: 2

Explanation

The OSPF broadcast network type is commonly used on Ethernet interfaces. Because multiple routers can share the same Ethernet segment, OSPF uses a Designated Router and Backup Designated Router to reduce the number of full adjacencies required. OSPF routers communicate using multicast addresses for neighbor discovery and protocol exchanges on these networks. The DR generates the Type 2 Network LSA representing the shared segment. Point-to-point networks do not require DR or BDR elections because only two routers participate. Understanding the default OSPF network type on Ethernet is important when troubleshooting neighbor states, DR elections, and adjacency formation.

Question 173

Which EIGRP command can be used to verify the EIGRP topology for a specific destination network?

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

Correct Answer: 1

Explanation

The show ip eigrp topology command can be used to examine EIGRP topology information for destinations and their available paths. By specifying a destination or other command options, administrators can focus on the routing information associated with a particular network. The output can show the successor, feasible distance, reported distance, and potential alternate paths. This makes the command useful for understanding why EIGRP selected a specific route. The neighbor command focuses on EIGRP peers, while the interface command focuses on EIGRP-enabled interfaces. When troubleshooting route selection, examining the topology table often provides information that cannot be seen from the routing table alone.

Question 174

Which BGP attribute is generally preferred when the AS Path lengths are equal and BGP reaches the Origin comparison?

1. Incomplete
2. EGP
3. IGP
4. MED

Correct Answer: 3

Explanation

The BGP Origin attribute has three commonly recognized values: IGP, EGP, and Incomplete. When BGP reaches the Origin comparison during best-path selection, IGP is generally preferred over EGP, and EGP is preferred over Incomplete. An IGP origin is commonly associated with a route introduced through a BGP network statement, while redistribution into BGP commonly produces an Incomplete origin. The Origin attribute is evaluated after several higher-priority path-selection criteria, so it does not automatically determine the best route. Understanding the order and meaning of Origin values is useful when two BGP paths have similar higher-priority attributes but different methods of route introduction.

Question 175

Which OSPF LSA type is generated by an ABR to advertise an ASBR’s reachability into another area?

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

Correct Answer: 1

Explanation

A Type 4 OSPF LSA, known as an ASBR Summary LSA, is generated by an ABR to provide information about how to reach an ASBR located in another area. This information is necessary when routers in one area need to reach external destinations advertised by an ASBR located elsewhere. The Type 5 LSA carries the external route itself, while the Type 4 LSA identifies the path toward the ASBR. Type 1 LSAs describe individual routers, and Type 2 LSAs describe multiaccess networks. Understanding the relationship between Type 4 and Type 5 LSAs is important when diagnosing external route reachability in multi-area OSPF networks.

Question 176

Which EIGRP packet type is used to reliably advertise a new route or route change?

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

Correct Answer: 2

Explanation

EIGRP Update packets are used to advertise new routes, changed routes, and route withdrawals to EIGRP neighbors. Important EIGRP routing information is delivered reliably, and the receiving router acknowledges the information as required. EIGRP does not periodically send the entire routing table in Update packets. Instead, it uses partial and bounded updates to communicate relevant changes. This helps reduce bandwidth consumption and supports efficient convergence. Hello packets maintain neighbor relationships, Query packets request information about alternative paths, and Reply packets answer Queries. When troubleshooting EIGRP convergence, examining Update activity can help determine whether routing changes are being properly propagated between neighbors.

Question 177

Which BGP attribute is normally used to make one external exit point more preferred for outbound traffic within an autonomous system?

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

Correct Answer: 2

Explanation

Local Preference is commonly used to select a preferred external exit point for outbound traffic within an autonomous system. A higher Local Preference value is normally preferred during BGP best-path selection. Because Local Preference is carried through internal BGP, multiple routers can follow the same routing policy. For example, an enterprise can assign a higher Local Preference to routes received from a primary provider and a lower value to routes received from a backup provider. AS-path prepending and MED are more commonly used to influence how external networks select inbound paths. Local Preference therefore provides a powerful mechanism for controlling outbound traffic across an autonomous system.

Question 178

Which OSPF state normally represents a fully synchronized adjacency?

1. Loading
2. Exchange
3. Full
4. Init

Correct Answer: 3

Explanation

The Full OSPF state indicates that two routers have completed database synchronization and have a fully established adjacency. At this stage, the routers have synchronized the relevant link-state information needed for their relationship. On point-to-point links, OSPF neighbors normally progress to Full. On broadcast networks, routers typically form Full adjacencies with the DR and BDR, while other routers may remain in the 2-Way state with each other. If an expected adjacency remains in Exchange or Loading, administrators should investigate database synchronization, MTU compatibility, packet loss, and LSA exchange. The Full state is therefore an important indicator of healthy OSPF adjacency formation.

Question 179

Which EIGRP mechanism determines whether an alternate route can be considered loop-free?

1. Administrative distance
2. Feasibility condition
3. Split horizon
4. Variance

Correct Answer: 2

Explanation

The EIGRP feasibility condition determines whether an alternate path can safely be considered a feasible successor. For the condition to be satisfied, the neighbor’s reported distance must be less than the local router’s feasible distance for that destination. This relationship provides a mathematical guarantee that the alternate path does not contain a routing loop under the EIGRP model. If the condition is satisfied, the route can be maintained as a feasible successor and may be used immediately when the current successor fails. If no feasible successor exists, EIGRP may need to query neighbors and perform additional DUAL calculations before finding another valid route.

Question 180

Which BGP attribute is normally used to make an advertised path appear longer to external BGP peers?

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

Correct Answer: 1

Explanation

The AS Path attribute can be manipulated through AS-path prepending to make an advertised route appear longer to external BGP peers. An autonomous system can add its own AS number multiple times to the AS Path when advertising a route. A receiving network may then consider that path less attractive compared with another route having a shorter AS Path, assuming other relevant attributes do not take precedence. This technique is primarily used to influence inbound traffic. It does not force external networks to select a particular path because each autonomous system controls its own BGP policies. AS-path prepending should therefore be viewed as a method of influencing external route selection rather than guaranteeing a specific traffic flow.