Cisco CCNP Enterprise 350-401 ENCOR EIGRP/OSPF Concepts and OSPF Implementation Practice Test

 

Topic 08 covers eigrp/ospf concepts and ospf implementation for the Cisco Certified Specialist – Enterprise Core certification. These original practice questions apply the verified 350-401 objectives to practical decisions and troubleshooting. Select one answer unless a fixed number is requested. For broader preparation, visit the Cisco 350-401 ENCOR Exam Dumps page. Each option includes an explanation of the relevant behavior and scenario constraints.

Question 1

A troubleshooting report says Router A uses EIGRP and stores neighbor-advertised destinations with metrics in a topology table, while Router B uses OSPF and maintains an area link-state database from flooded LSAs. Which classification is correct?

1. Both are pure link-state protocols because each can keep backup path information.
2. Both are distance-vector protocols because both have neighbors.
3. EIGRP uses DUAL; OSPF is link state and uses SPF.
4. OSPF is path-vector and EIGRP is link-state.
5. The protocols cannot be classified until administrative distance is known.

Correct Answer: C

 

Correct Answer

Answer C is correct because EIGRP learns distance information from neighbors and uses DUAL, while OSPF floods link-state information and computes routes from the resulting topology database.

Incorrect Answers

Answer A is incorrect because keeping alternate information does not make EIGRP a link-state protocol.

Answer B is incorrect because OSPF neighbors exchange/flood link-state information rather than only destination-distance vectors.

Answer D is incorrect because path-vector describes BGP behavior; the stated classification is reversed for EIGRP/OSPF.

Answer E is incorrect because administrative distance is a local route-source preference and does not define the routing algorithm family.

 

Question 2

A network engineer asks what topology knowledge each protocol maintains. Which statement best contrasts EIGRP and OSPF?

1. Neither protocol stores information beyond the routing table.
2. OSPF stores only the best next hop and discards other link-state information.
3. OSPF relies on the EIGRP topology table when both are configured.
4. EIGRP keeps neighbor-derived route metrics; OSPF synchronizes an area link-state database.
5. EIGRP stores a complete graph of every link in the autonomous system exactly like OSPF.

Correct Answer: D

 

Correct Answer

Answer D is correct because the protocols maintain different control-plane representations even though both ultimately install best routes in the RIB.

Incorrect Answers

Answer A is incorrect because both maintain protocol-specific state beyond installed routes. It does not satisfy the stem’s governing point: Protocol comparison should focus on the control-plane information each algorithm maintains.

Answer B is incorrect because OSPF retains LSAs in the LSDB and uses them to run SPF.

Answer C is incorrect because each routing protocol maintains its own control-plane database.

Answer E is incorrect because EIGRP does not build an OSPF-style synchronized LSDB of every area link.

 

Question 3

After a stable EIGRP adjacency is established, no topology changes occur for 20 minutes. A colleague expects a full routing table to be sent periodically every 30 seconds. Which correction is accurate?

1. Only OSPF can avoid periodic full-table updates; EIGRP cannot.
2. EIGRP must flood its complete topology table to all routers every hello interval.
3. EIGRP stops sending all protocol packets once routes are learned.
4. EIGRP sends updates when needed rather than periodic full-table updates.
5. The update interval is chosen from the OSPF dead timer.

Correct Answer: D

 

Correct Answer

Answer D is correct because EIGRP uses neighbor discovery/maintenance and bounded updates instead of periodically re-advertising the entire route set in steady state.

Incorrect Answers

Answer A is incorrect because EIGRP also avoids periodic full-table route advertisements. It does not satisfy the stem’s governing point: EIGRP uses neighbor-dependent, triggered/partial update behavior rather than periodic full routing-table advertisements.

Answer B is incorrect because hellos maintain neighbor relationships and do not imply full-table periodic flooding.

Answer C is incorrect because neighbor maintenance still uses hello traffic even without route changes.

Answer E is incorrect because OSPF timers do not control EIGRP update behavior.

 

Question 4

An enterprise divides OSPF into Area 0 plus three nonbackbone areas. Why is this hierarchy an OSPF design property rather than merely a naming convention?

1. Every area runs a different routing protocol.
2. Only Area 0 can contain routed interfaces.
3. ABRs carry reachability between bounded OSPF areas.
4. An area automatically creates a VRF.
5. Area IDs determine Ethernet VLAN tags.

Correct Answer: C

 

Correct Answer

Answer C is correct because routers within an area maintain synchronized topology for that area, while area boundaries limit how detailed topology is propagated.

Incorrect Answers

Answer A is incorrect because all areas are part of OSPF; the hierarchy scopes link-state information rather than selecting unrelated protocols.

Answer B is incorrect because nonbackbone areas contain routed OSPF interfaces as normal.

Answer D is incorrect because OSPF areas and VRF routing-table separation are different concepts.

Answer E is incorrect because OSPF area IDs are routing-control identifiers and do not tag Layer 2 frames.

 

Question 5

A router learns 10.50.0.0/16 from OSPF with metric 5 and from EIGRP with metric 1000. Both routes have default protocol administrative distances and are otherwise valid. Which value decides which protocol source is installed before comparing their unrelated metrics?

1. Administrative distance selects between the protocol sources; their metrics are not directly comparable.
2. The EIGRP autonomous-system number.
3. The larger prefix length only, even if the prefixes are identical.
4. The OSPF area number.
5. Whichever route has the numerically lower protocol metric, so OSPF always wins here.

Correct Answer: A

 

Correct Answer

Answer A is correct because the router first chooses among different route sources using administrative distance; an OSPF cost of 5 is not numerically compared with an EIGRP composite metric of 1000.

Incorrect Answers

Answer B is incorrect because the process/AS number identifies the EIGRP domain but does not establish interprotocol preference.

Answer C is incorrect because longest-prefix match matters between different destination lengths; here the same prefix is learned from two sources.

Answer D is incorrect because area membership does not replace administrative distance for route-source selection.

Answer E is incorrect because metrics from different protocols use different scales and are not directly compared across protocols.

 

Question 6

An EIGRP output for a route lists minimum bandwidth 100000 Kbit, total delay 300 microseconds, reliability 255/255, load 1/255, and MTU 1500. The question does not state modified K-values. Which approach is sound?

1. Assume load and reliability always contribute because they appear in the output.
2. Use MTU as the only EIGRP metric because it is displayed last.
3. Convert the OSPF cost formula into an EIGRP metric.
4. Use the configured EIGRP metric inputs and K-values.
5. Choose the route with the largest delay because EIGRP prefers larger metrics.

Correct Answer: D

 

Correct Answer

Answer D is correct because the vector metric output contains several values, but which components affect the composite metric depends on configured K-values; unspecified changes must not be assumed.

Incorrect Answers

Answer A is incorrect because visibility of a vector component does not prove the K-values weight it in the composite metric.

Answer B is incorrect because MTU is reported but is not simply the sole route metric.

Answer C is incorrect because EIGRP and OSPF use different metric systems. It does not satisfy the stem’s governing point: Interpret EIGRP metric inputs from stated K-values/configuration rather than inventing assumptions.

Answer E is incorrect because EIGRP prefers lower composite metrics, and delay treatment must follow the actual configuration.

 

Question 7

An OSPF router has two paths to 10.10.10.0/24. Path A crosses interfaces with OSPF costs 10, 20, and 5. Path B crosses costs 15 and 25. Which path is preferred, assuming all else is normal?

1. Path B with cost 25 because only the last interface matters.
2. Both are equal because they cross different numbers of routers.
3. The result cannot be known without EIGRP bandwidth values.
4. Path A with total cost 35.
5. Path B with cost 40 because OSPF prefers higher cost.

Correct Answer: D

 

Correct Answer

Answer D is correct because OSPF adds the outgoing interface costs along the path: 10 + 20 + 5 = 35, which is lower than Path B at 40.

Incorrect Answers

Answer A is incorrect because OSPF path cost is cumulative, not only the final hop.

Answer B is incorrect because hop count is not the direct OSPF metric; the explicitly supplied interface costs sum differently.

Answer C is incorrect because EIGRP inputs are irrelevant to an OSPF cost comparison when costs are already supplied.

Answer E is incorrect because OSPF selects the lower cumulative cost. It does not satisfy the stem’s governing point: OSPF path cost is the sum of the relevant interface costs, and lower total cost is preferred.

 

Question 8

A router has two EIGRP paths that both satisfy the feasibility condition. Their composite metrics are 1000 and 1500. With variance 1, only the 1000 path is installed. What concept distinguishes the default from a later configuration that could install both?

1. Equal-cost versus EIGRP unequal-cost load sharing using variance.
2. Administrative distance between two protocols.
3. OSPF DR election.
4. BGP multipath only.
5. MST instance load sharing.

Correct Answer: A

 

Correct Answer

Answer A is correct because variance 1 limits installation to equal-best metrics; a larger variance can admit feasible unequal-cost paths within the multiplier.

Incorrect Answers

Answer B is incorrect because both candidate paths are within EIGRP, so the question is intraprotocol load sharing.

Answer C is incorrect because DR/BDR roles do not control EIGRP path installation.

Answer D is incorrect because the scenario explicitly uses EIGRP, which supports unequal-cost load sharing under its own rules.

Answer E is incorrect because spanning tree is a Layer 2 control plane unrelated to EIGRP variance.

 

Question 9

Router R1 reaches a destination through R2 with feasible distance 200. R3 advertises the same destination with reported distance 150 and R1 would have total distance 260 through R3. Which statement about R3 is correct?

1. R3 qualifies as a feasible successor.
2. R3 is feasible only if OSPF also advertises the prefix.
3. R3 automatically becomes the successor because 150 is lower than 200.
4. R3 cannot be feasible because 260 is higher than 200.
5. Reported distance must be greater than feasible distance to prove loop freedom.

Correct Answer: A

 

Correct Answer

Answer A is correct because the feasibility condition tests the neighbor-reported distance against the current feasible distance, not whether the alternate total metric is lower than the successor.

Incorrect Answers

Answer B is incorrect because EIGRP feasibility is independent of an OSPF advertisement.

Answer C is incorrect because the successor is selected by the router total metric, and the stated total through R3 is 260.

Answer D is incorrect because an alternate can be a feasible successor even with a worse total metric if its reported distance satisfies the loop-free condition.

Answer E is incorrect because the feasibility condition requires reported distance to be less than the current feasible distance.

 

Question 10

A router has the exact same /24 prefix from an EIGRP internal route and an OSPF intra-area route. An operator notices the OSPF route has cost 2 while the EIGRP route metric is 28160. Which reasoning is correct?

1. Install EIGRP because larger metrics always have higher trust.
2. Install OSPF because 2 is numerically smaller than 28160.
3. Convert EIGRP 28160 into OSPF cost by dividing by 100.
4. Load share across both because both reach the same prefix.
5. Use administrative distance to choose between routes from different protocols.

Correct Answer: E

 

Correct Answer

Answer E is correct because the numeric metric scales are not comparable across routing protocols.

Incorrect Answers

Answer A is incorrect because trust between route sources is represented by administrative distance, not metric magnitude.

Answer B is incorrect because interprotocol route choice does not compare dissimilar protocol metric values directly.

Answer C is incorrect because there is no generic metric conversion for this selection process.

Answer D is incorrect because different route sources are not automatically combined just because the destination matches.

 

Question 11

An EIGRP successor link fails. The topology table already contains a feasible successor for the destination. What is the key convergence advantage?

1. EIGRP must always flood a new full link-state database before forwarding resumes.
2. DUAL can immediately use the known loop-free feasible successor without first querying neighbors.
3. The router must elect a DR before using the alternate.
4. Only OSPF supports a precomputed alternate path.
5. The failed route remains installed until the periodic 30-minute update.

Correct Answer: B

 

Correct Answer

Answer B is correct because a prequalified feasible successor avoids the active query process for that loss.

Incorrect Answers

Answer A is incorrect because EIGRP does not use an OSPF-style LSDB flood for this event.

Answer C is incorrect because DR election is an OSPF multiaccess concept. It does not satisfy the stem’s governing point: A feasible successor lets EIGRP converge locally after successor loss without a query computation.

Answer D is incorrect because EIGRP feasible successors specifically provide a loop-free backup mechanism.

Answer E is incorrect because EIGRP reacts to topology changes rather than waiting for a full periodic update.

 

Question 12

An OSPF link fails inside Area 10. Which statement best describes link-state propagation scope in a normal multi-area design?

1. Area 10 becomes a separate autonomous system after the failure.
2. The failure is propagated only by EIGRP queries.
3. No router outside the two directly connected endpoints learns any consequence.
4. The exact same internal link LSA must be flooded unchanged into every other OSPF area.
5. The detailed change floods inside Area 10; ABRs convey inter-area reachability beyond it.

Correct Answer: E

 

Correct Answer

Answer E is correct because OSPF areas bound detailed LSDB scope and use area boundary information for inter-area reachability.

Incorrect Answers

Answer A is incorrect because an area is still part of the same OSPF domain.

Answer B is incorrect because the scenario is OSPF, which uses LSAs and SPF.

Answer C is incorrect because the area does reconverge and inter-area reachability can change through ABR advertisements.

Answer D is incorrect because area boundaries intentionally limit detailed topology flooding. It does not satisfy the stem’s governing point: OSPF areas scope detailed link-state flooding while ABRs convey inter-area reachability.

 

Question 13

A design compares OSPF Area 20 as a normal area with an alternative restricted-area design that intentionally limits some external route information. Which statement is safe at ENCOR scope?

1. A normal area cannot connect to Area 0.
2. Restricted areas eliminate the need for an ABR.
3. Changing an area type automatically changes every interface IP address.
4. Area type changes which route information enters the area and must be configured consistently.
5. All OSPF area types flood every LSA type identically.

Correct Answer: D

 

Correct Answer

Answer D is correct because restricted area types are an OSPF design control, not merely a route-table display option.

Incorrect Answers

Answer A is incorrect because normal areas commonly connect to the backbone through ABRs.

Answer B is incorrect because area boundaries still require routers that connect the area to other OSPF areas.

Answer C is incorrect because area behavior is a routing-protocol configuration, not an addressing rewrite.

Answer E is incorrect because the purpose of stub/NSSA-style designs is to restrict certain external information.

 

Question 14

An enterprise wants to reduce inter-area route entries for sixteen contiguous /24 prefixes in Area 30. Where is the natural OSPF hierarchy boundary for that summarization?

1. On an EIGRP successor.
2. At the ABR advertising those Area 30 networks into another area.
3. Only on the DR of each Ethernet segment.
4. At any access switch, even if it does not run OSPF.
5. On every internal router inside Area 30 independently.

Correct Answer: B

 

Correct Answer

Answer B is correct because inter-area summarization is an area-boundary function because detailed intra-area topology is preserved inside the source area.

Incorrect Answers

Answer A is incorrect because EIGRP roles do not define OSPF area summarization.

Answer C is incorrect because DR election optimizes adjacency/flooding on a multiaccess segment and is not the area-summary boundary.

Answer D is incorrect because the summarizing function must be performed by the relevant OSPF boundary router.

Answer E is incorrect because ordinary inter-area summarization is not performed arbitrarily by every internal router.

 

Question 15

During an outage, OSPF recalculates a lower-cost path after an LSA change. Separately, the router also has an EIGRP route to the same prefix with a lower administrative distance than OSPF. Which concept determines the final steady-state installed source after both protocols converge?

1. Use administrative distance after each protocol computes its own best path.
2. OSPF path cost is compared numerically with the EIGRP composite metric.
3. The route with more hops must win.
4. The DR election decides which protocol is trusted.
5. Whichever protocol converged first permanently owns the route.

Correct Answer: A

 

Correct Answer

Answer A is correct because convergence finds each protocol candidate; route-source preference then decides which equal-prefix source enters the RIB.

Incorrect Answers

Answer B is incorrect because the metrics are protocol-specific scales. It does not satisfy the stem’s governing point: Convergence mechanics and steady-state route-source preference are separate decisions.

Answer C is incorrect because hop count is not a universal cross-protocol preference.

Answer D is incorrect because OSPF DR status is unrelated to interprotocol RIB preference.

Answer E is incorrect because arrival timing does not permanently override the stable route selection rules.

 

Question 16

R1 Gi0/0 is configured for OSPF area 0. R2 on the same Ethernet segment is configured for area 10. Hello/dead timers and IP subnet match. No adjacency forms. Which mismatch is decisive?

1. Match the OSPF area ID on the common link.
2. The interface costs must match.
3. The process IDs must match.
4. Both routers must become DR.
5. The routers need identical router IDs.

Correct Answer: A

 

Correct Answer

Answer A is correct because neighbors on the same link must agree on the area to form the intended adjacency.

Incorrect Answers

Answer B is incorrect because different OSPF interface costs can affect path choice but do not prevent adjacency by themselves.

Answer C is incorrect because OSPF process IDs are locally significant and do not need to be the same on neighbors.

Answer D is incorrect because only one DR and one BDR are elected on a broadcast network.

Answer E is incorrect because router IDs must be unique, not identical. It does not satisfy the stem’s governing point: Area mismatch on the link prevents the intended OSPF adjacency even when other parameters match.

 

Question 17

R1 and R2 share an Ethernet subnet. R1 uses OSPF hello/dead timers 10/40 seconds; R2 uses 1/4 seconds. Router IDs, area, authentication and MTU are otherwise compatible. What should be corrected?

1. Enable EIGRP on the interface.
2. Force both to priority 0.
3. Change the OSPF costs to match.
4. Make the OSPF hello and dead intervals compatible between the two neighbors.
5. Give both routers the same router ID.

Correct Answer: D

 

Correct Answer

Answer D is correct because OSPF neighbors require consistent timing expectations on the common link.

Incorrect Answers

Answer A is incorrect because another routing protocol does not fix the OSPF timer mismatch.

Answer B is incorrect because priority affects DR eligibility and does not reconcile hello/dead timers.

Answer C is incorrect because costs may differ without blocking the neighbor relationship.

Answer E is incorrect because duplicate router IDs are harmful and not the fix.

 

Question 18

R1 is 10.1.10.1/24 and R2 is configured 10.1.11.2/24 on the same Ethernet broadcast domain. OSPF is enabled in the same area and the physical interfaces are up. Why can the intended adjacency fail despite Layer 2 reachability?

1. R2 must have the lower IP address to become DR.
2. The interfaces must share an IPv4 subnet.
3. The routers must use /32 masks on Ethernet.
4. OSPF requires the host addresses to be numerically consecutive.
5. The OSPF process IDs must match the third octet.

Correct Answer: B

 

Correct Answer

Answer B is correct because a broadcast-link OSPF adjacency requires compatible IP addressing on the common subnet.

Incorrect Answers

Answer A is incorrect because DR election uses OSPF priority then router ID, and subnet mismatch is the earlier adjacency problem.

Answer C is incorrect because /32 would not establish the intended shared broadcast subnet.

Answer D is incorrect because neighbors do not need consecutive addresses, only compatible network parameters.

Answer E is incorrect because process IDs are local and unrelated to the IP subnet number.

 

Question 19

R1 Gi0/1 is configured as an OSPF passive interface. Its connected /24 is still advertised by the OSPF process, but a new router connected to Gi0/1 never appears as a neighbor. Why?

1. Passive interface shuts the physical port.
2. The neighbor must use a higher cost to overcome passive state.
3. Passive mode suppresses OSPF hellos while the connected network can still be advertised.
4. Passive interface converts OSPF into EIGRP.
5. Passive interface makes the router ID zero.

Correct Answer: C

 

Correct Answer

Answer C is correct because passive behavior prevents neighbor establishment without necessarily removing the prefix from the routing process.

Incorrect Answers

Answer A is incorrect because it changes routing-protocol behavior, not interface line protocol.

Answer B is incorrect because path cost does not enable OSPF hello transmission on a passive interface.

Answer D is incorrect because it is an OSPF configuration option, not a protocol conversion.

Answer E is incorrect because router ID selection is independent of a single passive-interface setting.

 

Question 20

Two routers on different links are both manually configured with OSPF router ID 10.255.255.1. The topology expects both to participate in the same OSPF domain. Which issue should be corrected?

1. Make the router IDs match every interface address.
2. Give both routers the same MAC address.
3. Make the router IDs unique.
4. Change only the OSPF process number on one router.
5. Use router ID 0.0.0.0 on one router.

Correct Answer: C

 

Correct Answer

Answer C is correct because OSPF router ID identifies a router within the domain; duplication can corrupt neighbor/LSA interpretation and must be removed.

Incorrect Answers

Answer A is incorrect because router ID is a 32-bit identifier and need not equal each interface address.

Answer B is incorrect because Layer 2 MAC duplication would create another problem and is unrelated to OSPF router-ID uniqueness.

Answer D is incorrect because process ID is locally significant and does not resolve a duplicate protocol router ID.

Answer E is incorrect because zero is not a valid intended unique router identity.

 

Question 21

Two routers are connected by a dedicated Ethernet link with no third device. The design wants no DR/BDR election and full adjacency directly between the two routers. Which OSPF network behavior fits?

1. Use nonbroadcast and remove all neighbor statements.
2. Use broadcast network type and set both priorities to 255.
3. Set one router priority 0 and leave the other broadcast.
4. Disable OSPF hellos after adjacency forms.
5. Configure the link for OSPF point-to-point network type.

Correct Answer: E

 

Correct Answer

Answer E is correct because point-to-point OSPF forms full adjacency directly and does not use a DR/BDR election.

Incorrect Answers

Answer A is incorrect because NBMA behavior is not the straightforward fit for a dedicated Ethernet link.

Answer B is incorrect because broadcast still invokes DR/BDR behavior. It does not satisfy the stem’s governing point: A direct two-router link can use OSPF point-to-point behavior to avoid unnecessary DR/BDR semantics.

Answer C is incorrect because that still leaves broadcast DR logic and does not make the link point-to-point.

Answer D is incorrect because neighbor maintenance requires OSPF control communication. It does not satisfy the stem’s governing point: A direct two-router link can use OSPF point-to-point behavior to avoid unnecessary DR/BDR semantics.

 

Question 22

Four OSPF routers share one broadcast Ethernet. R1/R2 priorities are 100 and 50; R3/R4 priorities are 1 and 0. Router IDs otherwise do not change the ordering. Which router is eligible and preferred as DR in a fresh election?

1. R4, because priority 0 is the strongest possible value.
2. R3, because default priority always overrides configured values.
3. R2, because the second-highest priority becomes DR.
4. All four become DR because Ethernet is multiaccess.
5. R1, because it has the highest nonzero OSPF interface priority.

Correct Answer: E

 

Correct Answer

Answer E is correct because broadcast DR election prefers the highest priority; priority 0 is ineligible.

Incorrect Answers

Answer A is incorrect because priority 0 explicitly makes a router ineligible for DR/BDR.

Answer B is incorrect because configured higher priorities outrank the default 1. It does not satisfy the stem’s governing point: Broadcast OSPF DR election prefers highest interface priority; priority 0 is ineligible.

Answer C is incorrect because the highest eligible priority becomes DR and the next candidate may become BDR.

Answer D is incorrect because a broadcast segment elects one DR and one BDR.

 

Question 23

On a broadcast Ethernet, R1 is DR, R2 is BDR, and R3/R4 are DROTHER. `show ip ospf neighbor` on R3 shows R4 in 2-WAY state while R1/R2 are FULL. Is R3-to-R4 necessarily broken?

1. No, because R3 and R4 have automatically formed an EIGRP adjacency instead.
2. Yes. Every OSPF neighbor on Ethernet must be FULL with every other router.
3. No. Two DROTHER routers normally stay 2-WAY while each becomes FULL with the DR and BDR.
4. Yes, unless both have priority 0.
5. Yes, because 2-WAY means the routers cannot hear each other at all.

Correct Answer: C

 

Correct Answer

Answer C is correct because OSPF reduces full-mesh database synchronization on broadcast networks by using DR/BDR adjacencies.

Incorrect Answers

Answer A is incorrect because the state shown is OSPF and does not imply EIGRP.

Answer B is incorrect because broadcast multiaccess OSPF intentionally leaves DROTHER pairs at 2-WAY.

Answer D is incorrect because DROTHER-to-DROTHER 2-WAY is normal regardless of whether their priority is zero or merely lower than the elected DR/BDR.

Answer E is incorrect because 2-WAY specifically means bidirectional hello communication has been established.

 

Question 24

R1 configures an Ethernet link as OSPF point-to-point. R2 on the same link is left at broadcast type. IP addressing, area and timers otherwise match. Neighbor formation is unstable/not as designed. What should be checked?

1. Make both routers use the same router ID.
2. Enable STP PortFast.
3. Make the OSPF network-type expectations compatible on both ends.
4. Configure LACP active mode.
5. Set both interface costs to zero.

Correct Answer: C

 

Correct Answer

Answer C is correct because network type affects hello parameters and adjacency/DR behavior; mismatched expectations are a direct troubleshooting target.

Incorrect Answers

Answer A is incorrect because router IDs should be unique, not equal. It does not satisfy the stem’s governing point: OSPF neighbors on a common link should use compatible network types and expectations.

Answer B is incorrect because spanning tree edge behavior is unrelated to OSPF network-type compatibility.

Answer D is incorrect because link aggregation negotiation does not reconcile OSPF network types.

Answer E is incorrect because zero is not a general OSPF cost fix and cost mismatch is not the stated network-type issue.

 

Question 25

On a broadcast OSPF segment, R1 has priority 200 and interface cost 100. R2 has priority 10 and interface cost 1. Which distinction is correct?

1. R2 cannot form an adjacency because its cost is lower than R1.
2. R2 becomes DR because lower interface cost always wins DR election.
3. R1 is favored for DR by priority; interface cost belongs to SPF path selection.
4. The two values are aliases displayed by different commands.
5. R1 path cost becomes 200 because priority replaces cost.

Correct Answer: C

 

Correct Answer

Answer C is correct because OSPF priority and cost influence different decisions. This directly matches the stem’s governing point: Separate OSPF DR priority from path-selection cost.

Incorrect Answers

Answer A is incorrect because neighbors can use different costs; that alone does not prevent adjacency.

Answer B is incorrect because DR election uses interface priority, then router ID, not OSPF path cost.

Answer D is incorrect because OSPF priority and OSPF cost have distinct functions.

Answer E is incorrect because priority and cost remain separate configuration values. It does not satisfy the stem’s governing point: Separate OSPF DR priority from path-selection cost.

 

Question 26

A company uses Area 0 and Area 10. Area 10 has one ABR with interfaces in both Area 10 and Area 0. Which design relationship is satisfied?

1. The ABR must be the DR on every Area 10 segment.
2. The nonbackbone area has a connection to the OSPF backbone through an ABR.
3. Area 10 operates as an independent autonomous system.
4. Area 0 can be omitted because Area 10 has only one ABR.
5. Every Area 10 router must also have a physical interface in Area 0.

Correct Answer: B

 

Correct Answer

Answer B is correct because normal multi-area OSPF uses Area 0 as the backbone interconnecting other areas through ABRs.

Incorrect Answers

Answer A is incorrect because ABR role is based on area membership, not DR election.

Answer C is incorrect because it remains part of the same OSPF domain.

Answer D is incorrect because the described hierarchy explicitly relies on the backbone.

Answer E is incorrect because only the ABR needs membership in both areas for ordinary connectivity.

 

Question 27

Router R5 has Gi0/0 in Area 0 and Gi0/1 in Area 20 within the same OSPF process. What role does that area membership make R5?

1. An autonomous system boundary router solely because it has two areas.
2. A DR for both areas automatically.
3. An EIGRP successor.
4. A Layer 2 root bridge.
5. An area border router (ABR).

Correct Answer: E

 

Correct Answer

Answer E is correct because a router with OSPF interfaces in the backbone and another area connects the areas and performs ABR functions.

Incorrect Answers

Answer A is incorrect because ASBR status depends on introducing routes from outside the OSPF domain, not simply area membership.

Answer B is incorrect because DR is elected per multiaccess segment and is not implied by ABR status.

Answer C is incorrect because the role is within OSPF. It does not satisfy the stem’s governing point: ABR identification follows OSPF interface membership in multiple areas including the backbone.

Answer D is incorrect because STP bridge roles are unrelated to OSPF area membership.

 

Question 28

A route appears as `O 10.20.1.0/24` on a router inside Area 20 and `O IA 10.30.1.0/24` on the same router. Which interpretation is correct?

1. `O IA` means the destination is inactive.
2. The codes determine DR/BDR status.
3. Both routes are EIGRP because `O` means outgoing.
4. The plain `O` route must be external to OSPF.
5. The plain `O` route is intra-area; `O IA` is inter-area.

Correct Answer: E

 

Correct Answer

Answer E is correct because Cisco route codes distinguish intra-area OSPF from OSPF inter-area routes.

Incorrect Answers

Answer A is incorrect because IA denotes inter-area, not inactive state. It does not satisfy the stem’s governing point: Differentiate OSPF intra-area and inter-area routes from route-table evidence.

Answer B is incorrect because route codes describe route source/type, not multiaccess neighbor role.

Answer C is incorrect because O is the OSPF route code. It does not satisfy the stem’s governing point: Differentiate OSPF intra-area and inter-area routes from route-table evidence.

Answer D is incorrect because external OSPF routes use different route codes such as E1/E2.

 

Question 29

Routers in Area 40 can reach every local area prefix and their LSDB is synchronized. They receive no inter-area routes. The ABR still has routes for Area 0, but its Area 40-facing configuration no longer advertises the expected summary LSAs. Where should investigation focus first?

1. Investigate the ABR inter-area advertisement because Area 40 local OSPF operation is healthy.
2. The area must elect a new Ethernet DR on every segment.
3. Enable EIGRP variance on the ABR.
4. Change all internal routes to static routes.
5. Every Area 40 internal link must be physically down.

Correct Answer: A

 

Correct Answer

Answer A is correct because the evidence isolates the failure to the boundary function rather than local adjacency or intra-area SPF.

Incorrect Answers

Answer B is incorrect because DR status does not generate all inter-area reachability; the ABR boundary evidence is more direct.

Answer C is incorrect because EIGRP load sharing does not restore missing OSPF inter-area LSAs.

Answer D is incorrect because that bypasses rather than diagnoses the missing OSPF boundary advertisement.

Answer E is incorrect because local reachability and synchronized LSDB contradict a broad internal failure.

 

Question 30

An engineer enables OSPF on Gi0/2 with `ip ospf 10 area 30`, but the design document says that subnet belongs to Area 0. Neighbors on the link are all in Area 0. Which correction is most direct?

1. Make Gi0/2 passive so it joins Area 0 silently.
2. Leave Area 30 and set cost 0.
3. Set the router ID to 0.0.0.30.
4. Change process 10 to process 0 because process ID must equal area ID.
5. Place Gi0/2 in Area 0 for that OSPF process.

Correct Answer: E

 

Correct Answer

Answer E is correct because the interface area association must match the intended neighbors and design.

Incorrect Answers

Answer A is incorrect because passive would suppress neighbor formation and still would not change the configured area.

Answer B is incorrect because cost does not resolve an area mismatch. It does not satisfy the stem’s governing point: OSPF interface area association must follow the intended link and neighbor area.

Answer C is incorrect because router ID does not determine an interface area assignment.

Answer D is incorrect because OSPF process ID is locally significant and need not equal the area number.

 

Question 31

Area 10 contains 10.10.8.0/24 through 10.10.11.0/24, with no other prefixes in 10.10.8.0/22 allocated anywhere. What is the smallest single summary that exactly covers those four contiguous /24s?

10. 10.10.8.0/22.
11. 10.10.8.0/23.
12. 10.10.8.0/21.
13. 10.10.0.0/16.
14. 10.10.10.0/23.

Correct Answer: A

 

Correct Answer

Answer A is correct because a /22 spans four /24s beginning on the binary boundary at third-octet 8: 8 through 11.

Incorrect Answers

Answer B is incorrect because a /23 covers only 8 and 9. It does not satisfy the stem’s governing point: Summarize only the explicitly contiguous prefix range and verify the binary boundary.

Answer C is incorrect because a /21 covers eight /24s, including 12-15 that are outside the stated range.

Answer D is incorrect because that is far broader than the explicitly bounded four /24s.

Answer E is incorrect because that covers 10 and 11 but omits 8 and 9.

 

Question 32

Area 20 contains sixteen contiguous /24 networks that should appear as one inter-area route in Area 0. Where should an `area 20 range …` style summary be configured?

1. On every Area 20 internal router.
2. On an access-layer Layer 2 switch not running OSPF.
3. On the broadcast DR only.
4. On the ABR for Area 20 under the OSPF process/address-family context.
5. On the Area 0 router with the highest router ID, regardless of area membership.

Correct Answer: D

 

Correct Answer

Answer D is correct because area-range summarization is performed at the area boundary when the ABR advertises inter-area reachability.

Incorrect Answers

Answer A is incorrect because internal routers retain the detailed intra-area topology; they are not all inter-area summary points.

Answer B is incorrect because a non-OSPF switch cannot originate the OSPF inter-area summary.

Answer C is incorrect because DR role controls multiaccess adjacency/flooding, not area-range summarization.

Answer E is incorrect because summary placement follows ABR area membership, not router-ID ordering.

 

Question 33

An ABR summarizes 10.20.0.0/16, but Area 30 actually contains only 10.20.1.0/24 and 10.20.2.0/24. Elsewhere, 10.20.200.0/24 is routed through a different domain. What is the design risk of advertising the broad /16 toward a region that prefers OSPF?

1. The /16 can attract traffic for unowned subprefixes and black-hole it without a more-specific route.
2. OSPF automatically creates every /24 inside the summary in Area 30.
3. The route can only affect EIGRP, not OSPF.
4. The summary forces all interfaces in Area 30 to use /16 masks.
5. The ABR becomes DR on every segment covered by the summary.

Correct Answer: A

 

Correct Answer

Answer A is correct because a summary asserts reachability for the whole covered prefix, so overbroad aggregation can attract traffic for ranges not actually reachable behind the summarizer.

Incorrect Answers

Answer B is incorrect because summarization does not create actual component networks. It does not satisfy the stem’s governing point: Avoid summaries that cover address space not genuinely reachable behind the summarizing boundary unless the design intentionally handles that traffic.

Answer C is incorrect because the summary is an OSPF advertisement and directly affects OSPF route selection.

Answer D is incorrect because route aggregation does not change interface addressing. It does not satisfy the stem’s governing point: Avoid summaries that cover address space not genuinely reachable behind the summarizing boundary unless the design intentionally handles that traffic.

Answer E is incorrect because DR election is unrelated to route-summary prefix length.

 

Question 34

A router applies a local inbound distribute list that prevents an OSPF-learned prefix from entering its routing table, but the router remains in the same area and the LSA still appears in its LSDB. Which distinction is correct?

1. Local route installation filtering is not the same as suppressing the LSA from the area link-state database.
2. The filter converts the route into an EIGRP route.
3. The filter must delete the LSA from every router in the area.
4. The only way to filter a route is to change its VLAN.
5. The prefix is no longer part of OSPF anywhere because one router filtered it.

Correct Answer: A

 

Correct Answer

Answer A is correct because routers in the same area require a consistent LSDB; some filtering mechanisms affect the RIB without removing the underlying LSA from intra-area flooding.

Incorrect Answers

Answer B is incorrect because route filtering does not change protocol ownership. It does not satisfy the stem’s governing point: Distinguish local route filtering from suppression of link-state information in an OSPF area.

Answer C is incorrect because local RIB filtering does not imply topology information vanishes area-wide.

Answer D is incorrect because Layer 2 VLAN configuration is unrelated to OSPF route installation policy.

Answer E is incorrect because one local route policy does not rewrite all other routers LSDBs.

 

Question 35

A prefix list used for an OSPF boundary filter contains `permit 10.30.0.0/16 ge 24 le 24`. Which candidate route matches this entry?

10. 10.30.44.0/24.
11. 10.30.0.0/16.
12. 10.30.0.0/15.
13. 10.30.44.0/25.
14. 10.31.44.0/24.

Correct Answer: A

 

Correct Answer

Answer A is correct because it is contained within 10.30.0.0/16 and has exactly /24 prefix length, satisfying ge 24 and le 24.

Incorrect Answers

Answer B is incorrect because its /16 length does not meet the minimum /24 requirement.

Answer C is incorrect because it is both broader than the base range and has the wrong prefix length.

Answer D is incorrect because /25 exceeds the configured maximum /24. It does not satisfy the stem’s governing point: Read both containment and prefix-length conditions in a supplied route filter.

Answer E is incorrect because it is outside the base 10.30.0.0/16 range. It does not satisfy the stem’s governing point: Read both containment and prefix-length conditions in a supplied route filter.

 

Question 36

A router uses `router ospfv3 10` and enters `address-family ipv6 unicast`. Which interpretation is correct?

10. It assigns area 10 automatically because the process ID is 10.
11. It configures a VRF named ipv6.
12. The configuration is selecting the IPv6 unicast address family within the OSPFv3 process.
13. It disables IPv6 on all interfaces until an IPv4 address is added.
14. It converts the process into OSPFv2 for IPv4 only.

Correct Answer: C

 

Correct Answer

Answer C is correct because OSPFv3 supports address-family contexts, and the command explicitly enters IPv6 unicast AF configuration.

Incorrect Answers

Answer A is incorrect because OSPF process ID and area ID are separate values.

Answer B is incorrect because address-family context is a routing-protocol AF, not a VRF creation command.

Answer D is incorrect because the purpose is to configure IPv6 OSPFv3 behavior, not disable IPv6.

Answer E is incorrect because the command explicitly identifies the IPv6 AF under OSPFv3.

 

Question 37

`show ospfv3 neighbor` lists a neighbor next hop as FE80::A8BB:CCFF:FE00:6F00 on Gi0/0. Which statement best explains the address?

1. The address identifies the OSPF area number in hexadecimal.
2. OSPFv3 can use a link-local neighbor address that is valid only on the local link.
3. The address must be advertised unchanged across every router hop.
4. The neighbor is unreachable because OSPFv3 requires a globally routed next-hop address.
5. FE80:: proves the route is an IPv4-mapped address.

Correct Answer: B

 

Correct Answer

Answer B is correct because link-local addresses are valid for local-link control communication and are scoped to the interface/link.

Incorrect Answers

Answer A is incorrect because area identification is separate from the IPv6 neighbor link-local address.

Answer C is incorrect because link-local addresses are not forwarded across links. It does not satisfy the stem’s governing point: OSPFv3 neighbor relationships can use interface-scoped IPv6 link-local addresses.

Answer D is incorrect because OSPFv3 commonly uses link-local neighbor addressing on the shared link.

Answer E is incorrect because FE80::/10 is the IPv6 link-local prefix, not an IPv4-mapped format.

 

Question 38

R1 and R2 show an OSPFv3 FULL adjacency on their shared link. R1 still cannot ping R2 global IPv6 loopback 2001:db8:2::2/128. Which troubleshooting conclusion is best?

1. Disable IPv6 unicast routing so OSPFv3 can forward directly.
2. The FULL state proves the loopback ping must succeed, so the output is impossible.
3. Verify advertisement and return routing for the loopback; FULL adjacency alone is insufficient.
4. Replace the link-local neighbor addresses with identical global addresses.
5. Change the OSPFv3 process ID to 128 because the loopback is /128.

Correct Answer: C

 

Correct Answer

Answer C is correct because a healthy neighbor relationship establishes control-plane adjacency on one link, but the target prefix still needs routing and forwarding reachability.

Incorrect Answers

Answer A is incorrect because disabling routing would not improve routed reachability. It does not satisfy the stem’s governing point: Verify routed prefix advertisement and forwarding separately from a healthy OSPFv3 adjacency.

Answer B is incorrect because adjacency and end-to-end data reachability are related but distinct.

Answer D is incorrect because unique addressing and route advertisement, not identical addresses, are required.

Answer E is incorrect because process ID is locally significant and unrelated to prefix length.

 

Question 39

The OSPFv3 process and IPv6 AF are configured, but Gi0/2 has IPv6 enabled and never appears in `show ospfv3 interface`. The design expects Gi0/2 in Area 0. What configuration class should be checked first?

1. Whether the EIGRP variance is high enough.
2. Whether the interface is the STP root port.
3. Whether Gi0/2 has the lowest MAC address.
4. Whether DTP negotiated a trunk.
5. Check whether Gi0/2 is enabled for the correct OSPFv3 process, area, and address family.

Correct Answer: E

 

Correct Answer

Answer E is correct because an interface must participate in the process/area to exchange OSPFv3 control traffic; global process configuration alone does not attach every interface.

Incorrect Answers

Answer A is incorrect because EIGRP settings do not enable OSPFv3 on an interface.

Answer B is incorrect because STP role does not attach a Layer 3 interface to OSPFv3.

Answer C is incorrect because MAC ordering does not determine OSPFv3 process participation.

Answer D is incorrect because OSPFv3 interface participation is not created by Layer 2 trunk negotiation.

 

Question 40

Two OSPF neighbors on a point-to-point Ethernet repeatedly reach EXSTART/EXCHANGE and reset. Debug output reports a DBD MTU mismatch: R1 interface MTU 1500, R2 MTU 1400. Which correction addresses the evidence most directly?

1. Change both router IDs to the same value.
2. Increase the OSPF cost on R2.
3. Set both OSPF priorities to zero.
4. Enable BPDU guard on both router interfaces.
5. Make the neighboring interface MTUs compatible before changing unrelated OSPF settings.

Correct Answer: E

 

Correct Answer

Answer E is correct because OSPF database exchange can fail when neighbors advertise incompatible interface MTU values; correcting the underlying mismatch is the clean fix.

Incorrect Answers

Answer A is incorrect because duplicate router IDs create a different problem and do not solve the MTU discrepancy.

Answer B is incorrect because cost affects route preference after adjacency and does not resolve DBD MTU validation.

Answer C is incorrect because priority affects DR election and is irrelevant on the stated point-to-point behavior.

Answer D is incorrect because BPDU guard is a Layer 2 spanning-tree edge protection feature, not an OSPF MTU fix.