CCNA OSPF Questions

Matchingmedium

Drag and drop each OSPF packet type on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Discovers neighbors and maintains adjacency state

Contains a list of LSA headers for database synchronization

Requests specific LSAs from a neighbor

Sends one or more complete LSAs to a neighbor

Confirms receipt of LSU packets

Why these pairings

Hello packets discover and maintain neighbor relationships; DBD packets contain a summary of the LSDB; LSR packets request specific LSAs; LSU packets send full LSAs in response to LSRs; LSAck packets acknowledge receipt of LSUs.

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Drag & Dropmedium

Drag and drop the steps of OSPF virtual link configuration into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

A virtual link connects a non-backbone area to Area 0 through a transit area. First, identify the ABR with the transit area, then configure the virtual link on both ABRs using the router ID of the neighbor, ensure the transit area has full OSPF adjacency, and finally verify the virtual link is operational.

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MCQhard

A network engineer is troubleshooting an OSPF issue where a router is not learning a route to a network that is advertised via a type 5 LSA from an ASBR. The engineer checks the OSPF database and sees the type 5 LSA, but the route is not in the routing table. The forwarding address in the LSA is 0.0.0.0. What is the most likely cause?

A.The ASBR is not reachable via an OSPF internal route.

B.The type 5 LSA has a metric of 16777215.

C.The OSPF process ID on the ASBR is different from the other routers.

D.The type 5 LSA is being filtered by an outbound route filter.

AnswerA

Correct because OSPF requires the ASBR to be reachable via an intra-area or inter-area route for the type 5 LSA to be installed.

Why this answer

When a Type 5 LSA has a forwarding address of 0.0.0.0, OSPF routers will use the ASBR as the next hop for the external route. For the route to be installed in the routing table, the ASBR must be reachable via an OSPF intra-area or inter-area route. If the ASBR is not reachable (e.g., no valid OSPF route to the ASBR's router ID), the Type 5 LSA is considered unreachable and is not installed, even though it exists in the OSPF database.

Exam trap

Cisco often tests the misconception that a Type 5 LSA present in the database automatically guarantees the route is installed, but the trap here is that the forwarding address of 0.0.0.0 requires the ASBR to be reachable via an OSPF internal route, which is a common oversight.

How to eliminate wrong answers

Option B is wrong because a metric of 16777215 (the maximum OSPF metric) would cause the route to be considered unreachable, but the question states the LSA is present in the database and the forwarding address is 0.0.0.0, not that the metric is invalid. Option C is wrong because OSPF process IDs are locally significant and do not affect the exchange of LSAs or route installation between routers; different process IDs on different routers do not prevent route learning. Option D is wrong because an outbound route filter would prevent the LSA from being sent or received, but the engineer confirms the Type 5 LSA is present in the database, meaning it was not filtered.

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Drag & Dropmedium

Drag and drop the steps of OSPF SPF calculation steps (Dijkstra) into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

The Dijkstra algorithm first initializes the candidate list with the root node, then iteratively moves the lowest-cost candidate to the tree, updating neighbor costs, and finally builds the routing table from the shortest-path tree.

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MCQhard

A network engineer is troubleshooting an OSPF adjacency issue between two routers connected via a Frame Relay network. The adjacency is stuck in the 2WAY state. The engineer has verified that the routers are in the same area and have matching hello/dead intervals. What is the most likely cause?

A.The OSPF network type is non-broadcast and the neighbors are not manually configured.

B.The OSPF router priority is set to 0 on both routers.

C.The OSPF area ID is different.

D.The Frame Relay map is missing for the broadcast keyword.

AnswerA

Correct because in non-broadcast networks, OSPF neighbors must be manually configured; otherwise, the adjacency will remain in 2WAY.

Why this answer

In OSPF over Frame Relay, the default network type for physical interfaces is non-broadcast (NBMA). On an NBMA network, OSPF does not send multicast Hello packets; instead, neighbors must be manually configured using the 'neighbor' command. Without manual neighbor configuration, the routers will not proceed past the 2WAY state because they cannot form a full adjacency without explicit neighbor discovery.

Exam trap

The trap here is that candidates often assume the 2WAY state is normal or that it indicates a DR/BDR election issue, but in NBMA networks it specifically indicates that OSPF is not attempting to form a full adjacency because neighbors are not manually defined.

How to eliminate wrong answers

Option B is wrong because setting the router priority to 0 on both routers prevents one from becoming the DR/BDR, but the adjacency can still form and reach FULL state (it will be a 2-way adjacency with no DR/BDR election). Option C is wrong because the engineer has already verified that the routers are in the same area, so mismatched area IDs would cause the adjacency to get stuck in INIT or EXSTART, not 2WAY. Option D is wrong because the missing 'broadcast' keyword in the Frame Relay map would affect multicast forwarding, but on a non-broadcast network type, OSPF does not rely on multicast; the core issue is the lack of manual neighbor configuration, not the broadcast keyword.

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MCQmedium

Examine this OSPF configuration on router R4: interface GigabitEthernet0/0 ip address 172.16.1.4 255.255.255.0 ip ospf 1 area 0 ip ospf cost 50 ! router ospf 1 router-id 4.4.4.4 network 172.16.0.0 0.0.255.255 area 0 What is the OSPF cost of the GigabitEthernet0/0 interface?

A.50

B.1 (default for GigabitEthernet)

C.100 (derived from reference bandwidth 100 Mbps / 1 Gbps)

D.10 (derived from reference bandwidth 1000 Mbps / 100 Mbps)

AnswerA

The cost is explicitly set to 50 with the 'ip ospf cost' command.

Why this answer

The OSPF cost of an interface is determined by the `ip ospf cost` command, which explicitly overrides the default cost calculation based on reference bandwidth. Since R4's GigabitEthernet0/0 interface has `ip ospf cost 50` configured under it, the cost is set to 50 regardless of the interface bandwidth or reference bandwidth settings.

Exam trap

Cisco often tests the precedence of the `ip ospf cost` command over the default cost calculation, trapping candidates who assume the default cost for GigabitEthernet (1) or who incorrectly calculate the cost using the reference bandwidth formula without considering the explicit configuration.

How to eliminate wrong answers

Option B is wrong because the default OSPF cost for a GigabitEthernet interface is not 1; the default cost is calculated as reference bandwidth (default 100 Mbps) divided by interface bandwidth (1000 Mbps), which equals 1 only if the reference bandwidth is set to 1000 Mbps. Option C is wrong because the cost derived from the default reference bandwidth (100 Mbps) divided by 1 Gbps would be 0.1, which is not a valid OSPF cost (costs are integers, and Cisco rounds up to 1). Option D is wrong because the calculation of 1000 Mbps / 100 Mbps equals 10, but this would only apply if the reference bandwidth were changed to 1000 Mbps and the interface bandwidth were 100 Mbps, which does not match the GigabitEthernet interface's actual bandwidth of 1 Gbps.

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Multi-Selecthard

Which three statements about OSPF LSA types are true? (Choose three.)

Select 3 answers

A.Type 1 LSAs are generated by every OSPF router to describe its own interfaces and neighbors.

B.Type 2 LSAs are generated by the Designated Router on multiaccess networks.

C.Type 5 LSAs are generated by ASBRs to advertise routes from other routing domains.

D.Type 3 LSAs are generated by ASBRs to summarize routes between areas.

E.Type 4 LSAs are generated by the ASBR to advertise its presence to other areas.

AnswersA, B, C

Correct because Router LSAs (Type 1) are created by each router to advertise its directly connected links.

Why this answer

Option A is correct because Type 1 LSAs (Router LSAs) are generated by every router and describe the router's directly attached links. Option B is correct because Type 2 LSAs (Network LSAs) are generated by the DR on broadcast and NBMA networks to describe the segment and attached routers. Option C is correct because Type 5 LSAs (AS External LSAs) are generated by ASBRs to advertise external routes.

Option D is incorrect because Type 3 LSAs (Summary LSAs) are generated by ABRs, not ASBRs. Option E is incorrect because Type 4 LSAs (ASBR Summary LSAs) are generated by ABRs, not the ASBR itself.

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Multi-Selectmedium

Which three statements about OSPF route summarization are true? (Choose three.)

Select 3 answers

A.Inter-area route summarization is configured on ABRs using the "area range" command.

B.External route summarization is configured on ASBRs using the "summary-address" command.

C.Route summarization reduces the size of the LSDB and improves network convergence.

D.Route summarization can be configured on any OSPF router to reduce Type 1 LSAs.

E.Summarization in OSPF can be applied to Type 1 and Type 2 LSAs to reduce flooding.

AnswersA, B, C

Correct because ABRs use the "area range" command to summarize routes between areas, reducing Type 3 LSAs.

Why this answer

Option A is correct because inter-area summarization is configured on ABRs to reduce the number of Type 3 LSAs. Option B is correct because external route summarization is configured on ASBRs to reduce Type 5 LSAs. Option C is correct because summarization helps reduce the routing table size and LSA flooding, improving network stability.

Option D is incorrect because summarization is not supported on internal routers; it is only performed on ABRs and ASBRs. Option E is incorrect because summarization does not affect Type 1 or Type 2 LSAs; it only affects Type 3 and Type 5 LSAs.

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Matchingmedium

Drag and drop each OSPF area type on the left to its matching characteristic on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Must connect all other areas; area 0

Blocks Type 5 LSAs; allows Type 3 summary LSAs

Blocks Type 5 and Type 3 LSAs; uses default route only

Allows Type 7 LSAs for external routes; blocks Type 5 LSAs

Blocks Type 5 and Type 3; allows Type 7 for external routes

Why these pairings

Backbone area (0) connects all other areas; Stub area blocks Type 5 LSAs but allows Type 3; Totally stubby area blocks both Type 5 and Type 3 (default route only); NSSA allows Type 7 LSAs for external routes but blocks Type 5; NSSA totally stubby blocks Type 5 and Type 3 but allows Type 7.

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MCQmedium

Router R3 has the following OSPF configuration: router ospf 1 router-id 3.3.3.3 network 10.0.0.0 0.255.255.255 area 0 default-information originate always metric 20 metric-type 2 What is the effect of the 'default-information originate always' command?

A.It redistributes all connected routes into OSPF.

B.It injects a default route into OSPF only if a default route is present in the routing table.

C.It injects a default route into OSPF unconditionally, with metric 20 and type E2.

D.It sets the OSPF router ID to 3.3.3.3 and enables default route filtering.

AnswerC

The 'always' keyword makes the default route always injected, with specified metric and type.

Why this answer

The 'default-information originate always' command injects a default route (0.0.0.0/0) into the OSPF link-state database unconditionally, regardless of whether the router itself has a default route in its routing table. The 'always' keyword overrides the default behavior, which requires a pre-existing default route. The metric 20 and metric-type 2 (E2) are explicitly set in the command, making the injected route an external type 2 route with a seed metric of 20.

Exam trap

Cisco often tests the distinction between the default behavior (inject only if a default route exists) and the 'always' keyword (unconditional injection), leading candidates to mistakenly think 'always' is required for any default route injection or that it modifies the metric behavior.

How to eliminate wrong answers

Option A is wrong because 'default-information originate' injects a default route, not all connected routes; redistributing connected routes requires the 'redistribute connected' command under OSPF. Option B is wrong because the 'always' keyword makes the injection unconditional; without 'always', the command would require a default route in the routing table, but with 'always' it does not. Option D is wrong because the 'router-id 3.3.3.3' is a separate configuration line that sets the OSPF router ID, and the 'default-information originate' command does not enable any filtering; it injects a default route.

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MCQhard

A network engineer runs the following command on Router R7: R7# show ip ospf virtual-links Virtual Link OSPF_VL0 to router 2.2.2.2 is up Run as demand circuit DoNotAge LSA allowed. Transit area 1, via interface GigabitEthernet0/1, Cost of using 10 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:07 Adjacency State FULL Based on this output, what can be concluded?

A.The virtual link is used to connect area 0 to a non-backbone area.

B.Router 2.2.2.2 is the other endpoint of the virtual link.

C.The virtual link is down.

D.The virtual link uses area 0 as the transit area.

AnswerB

The virtual link is to router 2.2.2.2, so that is the remote endpoint.

Why this answer

The output shows that the virtual link OSPF_VL0 to router 2.2.2.2 is up and the adjacency state is FULL. This confirms that router 2.2.2.2 is the remote endpoint of the virtual link, as the command displays the router ID of the neighbor at the other end of the virtual link.

Exam trap

Cisco often tests the misconception that the router ID shown in the virtual link output is the local router's ID, when in fact it is the remote endpoint's router ID, as confirmed by the 'to router' syntax in the command output.

How to eliminate wrong answers

Option A is wrong because the virtual link is used to connect a non-backbone area to area 0, not to connect area 0 to a non-backbone area; the virtual link extends area 0 into a transit area. Option C is wrong because the output explicitly states 'Virtual Link ... is up' and 'Adjacency State FULL', indicating the link is operational. Option D is wrong because the transit area is area 1, not area 0; the output shows 'Transit area 1'.

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MCQeasy

A network engineer is troubleshooting an OSPF adjacency issue between two routers connected via a serial link. The adjacency is stuck in the INIT state. The engineer has verified that the IP addresses are in the same subnet and that the link is up. What is the most likely cause?

A.The OSPF router IDs are the same.

B.The OSPF hello interval is mismatched between the two routers.

C.The OSPF process ID is different.

D.The OSPF network type is point-to-point on one router and point-to-multipoint on the other.

AnswerB

Correct because if the hello intervals are different, the routers will not agree on the hello timer, causing the adjacency to remain in INIT.

Why this answer

The INIT state in OSPF indicates that a router has received a Hello packet from its neighbor but the neighbor has not yet seen its own Router ID in the received Hello. A mismatched Hello interval causes the routers to send Hellos at different rates, so one router may not receive a Hello within the expected Dead interval, preventing the neighbor from seeing its Router ID in the received Hello and thus stalling the adjacency in INIT.

Exam trap

Cisco often tests the distinction between INIT and other OSPF states, and the trap here is that candidates confuse a network type mismatch (which causes EXSTART issues) with a Hello interval mismatch (which causes INIT), or incorrectly assume that the OSPF process ID must match.

How to eliminate wrong answers

Option A is wrong because identical OSPF router IDs would cause a conflict that typically results in the adjacency being stuck in EXSTART/EXCHANGE or a neighbor state of DOWN, not INIT. Option C is wrong because the OSPF process ID is locally significant and does not need to match between routers for adjacency formation. Option D is wrong because a network type mismatch (e.g., point-to-point vs. point-to-multipoint) usually causes the adjacency to get stuck in the EXSTART state due to DR/BDR election issues, not in INIT.

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MCQmedium

Router R5 has the following OSPF configuration: router ospf 1 router-id 5.5.5.5 network 10.0.0.0 0.255.255.255 area 0 area 0 authentication message-digest ! interface GigabitEthernet0/0 ip address 10.1.1.5 255.255.255.0 ip ospf message-digest-key 1 md5 cisco123 What is missing from this OSPF authentication configuration?

A.The configuration is complete and correct.

B.The interface needs the 'ip ospf authentication message-digest' command.

C.The 'area 0 authentication' command should be 'area 0 authentication md5'.

D.The 'network' command should include the area authentication keyword.

AnswerB

This command activates MD5 authentication on the interface, required for the area authentication to take effect.

Why this answer

Option B is correct because OSPF authentication configuration requires two components: an area-level authentication type (configured via `area 0 authentication message-digest`) and an interface-level authentication mode (configured via `ip ospf authentication message-digest`). The interface command tells the OSPF process to actually use the key defined with `ip ospf message-digest-key`. Without it, the interface defaults to no authentication, even though the area is configured for authentication.

Exam trap

The trap here is that candidates assume configuring the area authentication and the key is sufficient, overlooking the mandatory interface-level `ip ospf authentication message-digest` command that activates authentication on the specific interface.

How to eliminate wrong answers

Option A is wrong because the configuration is incomplete; the interface lacks the `ip ospf authentication message-digest` command, so OSPF packets on GigabitEthernet0/0 will not be authenticated. Option C is wrong because `area 0 authentication md5` is not a valid Cisco IOS command; the correct syntax is `area 0 authentication message-digest`. Option D is wrong because the `network` command does not support an area authentication keyword; area authentication is configured separately under the OSPF process or on the interface.

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MCQhard

A network engineer issues the following command on Router R2: R2# show ip ospf interface GigabitEthernet0/0 GigabitEthernet0/0 is up, line protocol is up Internet Address 192.168.1.2/24, Area 0 Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2 Backup Designated router (ID) 1.1.1.1, Interface address 192.168.1.1 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:03 Index 1/1/1, flood queue length 0 Next 0x0(0)/0x0(0)/0x0(0) Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 1.1.1.1 (Backup Designated Router) Adjacent with neighbor 3.3.3.3 Based on this output, what can be concluded?

A.R2 has a full OSPF adjacency with all neighbors on this segment.

B.R2 is the Backup Designated Router on this segment.

C.The OSPF cost to reach the network 192.168.1.0/24 is 20.

D.R2 will send hello packets every 40 seconds.

AnswerA

The adjacent neighbor count is 2, equal to the neighbor count, meaning all neighbors are fully adjacent.

Why this answer

The output shows that R2 is the Designated Router (DR) on this broadcast segment, with two neighbors listed: 1.1.1.1 (BDR) and 3.3.3.3. The 'Adjacent neighbor count is 2' and both neighbors are listed as 'Adjacent with neighbor', confirming that R2 has formed full OSPF adjacencies with all neighbors on this segment. In OSPF broadcast networks, only the DR and BDR form full adjacencies with all routers, while non-DR/BDR routers only form full adjacencies with the DR and BDR.

Exam trap

Cisco often tests the distinction between 'neighbor count' and 'adjacent neighbor count' — candidates may incorrectly assume that all neighbors are fully adjacent, but in broadcast networks, only the DR and BDR have full adjacencies with all routers, while other routers only have full adjacency with the DR and BDR.

How to eliminate wrong answers

Option B is wrong because R2 is the Designated Router (State DR, Priority 1), not the Backup Designated Router; the BDR is 1.1.1.1. Option C is wrong because the cost shown (Cost: 10) is the OSPF cost of the GigabitEthernet0/0 interface on R2, not the cost to reach the network 192.168.1.0/24; the cost to reach that network would be the sum of outgoing interface costs along the path. Option D is wrong because the Hello timer is configured as 10 seconds (Hello 10), not 40 seconds; the Dead timer is 40 seconds.

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Matchingmedium

Drag and drop each OSPF network type on the left to its matching DR election behavior on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Elects a DR/BDR; uses multicast Hellos (224.0.0.5 and 224.0.0.6)

Elects a DR/BDR; requires manual neighbor configuration

No DR/BDR election; uses multicast Hellos (224.0.0.5)

No DR/BDR election; treats each neighbor as a point-to-point link

No DR/BDR election; requires manual neighbor configuration

Why these pairings

Broadcast network type (e.g., Ethernet) elects a DR/BDR. Non-broadcast (NBMA) also elects DR/BDR but requires manual neighbor configuration. Point-to-point does not elect a DR/BDR.

Point-to-multipoint does not elect a DR/BDR. Point-to-multipoint non-broadcast does not elect a DR/BDR and requires manual neighbor configuration.

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MCQmedium

A network engineer runs the following command on Router R3: R3# show ip route ospf Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP a - application route + - replicated route, % - next hop override Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks O IA 10.1.1.0/24 [110/20] via 192.168.1.1, 00:12:34, GigabitEthernet0/0 O 10.2.2.0/24 [110/10] via 192.168.1.2, 00:15:22, GigabitEthernet0/0 O E2 10.3.3.0/24 [110/20] via 192.168.1.3, 00:08:11, GigabitEthernet0/0 Based on this output, what can be concluded?

A.The route to 10.3.3.0/24 is an external route redistributed into OSPF.

B.The route to 10.1.1.0/24 is in the same OSPF area as R3.

C.The metric for 10.3.3.0/24 includes the internal cost to the ASBR.

D.R3 is an ASBR.

AnswerA

O E2 indicates an OSPF external route of type 2, typically redistributed from another routing protocol.

Why this answer

The route to 10.3.3.0/24 is marked as 'O E2' in the output, which stands for OSPF external type 2. This indicates that the route was redistributed into OSPF from another routing protocol or a different OSPF process, making it an external route. The 'E2' designation confirms it is an external route with a fixed metric that does not include the internal cost to the ASBR.

Exam trap

Cisco often tests the difference between OSPF external type 1 (E1) and type 2 (E2) routes, specifically that E2 routes do not include the internal cost to the ASBR, which is a common misconception that leads candidates to incorrectly select option C.

How to eliminate wrong answers

Option B is wrong because the route to 10.1.1.0/24 is marked as 'O IA' (OSPF inter-area), which means it originates from a different OSPF area than R3, not the same area. Option C is wrong because for an OSPF external type 2 (E2) route, the metric shown (20) is the external metric only and does not include the internal cost to the ASBR; that behavior is specific to external type 1 (E1) routes. Option D is wrong because R3 is simply receiving these OSPF routes; there is no indication in the output that R3 is redistributing routes into OSPF, which would be required for it to be an ASBR.

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Matchingmedium

Drag and drop each OSPF area type on the left to its matching characteristic on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Must connect all other areas and cannot be a stub

Blocks Type 5 LSAs; uses a default route for external destinations

Blocks Type 3 and Type 5 LSAs; uses a default route for all inter-area and external destinations

Allows Type 7 LSAs for external routes; ABR translates them to Type 5

Permits all LSA types including Type 3, 4, and 5

Why these pairings

The backbone area (Area 0) connects all other areas. A stub area blocks Type 5 LSAs and uses a default route. A totally stubby area blocks both Type 3 and Type 5 LSAs, using only a default route.

An NSSA (Not-So-Stubby Area) allows Type 7 LSAs for external routes and converts them to Type 5 at the ABR.

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MCQeasy

What is the default OSPF hello interval on a broadcast multi-access network (e.g., Ethernet)?

A.5 seconds

B.10 seconds

C.30 seconds

D.40 seconds

AnswerB

The default hello interval for broadcast and point-to-point networks is 10 seconds.

Why this answer

On broadcast multi-access networks like Ethernet, OSPF defaults to a hello interval of 10 seconds. This is defined in RFC 2328 and is used to maintain neighbor relationships and detect failures quickly. The corresponding dead interval is 40 seconds (4 times the hello interval).

Exam trap

Cisco often tests the distinction between hello and dead intervals, and the trap here is confusing the default dead interval (40 seconds) with the hello interval (10 seconds) on broadcast multi-access networks.

How to eliminate wrong answers

Option A is wrong because 5 seconds is the default hello interval for OSPF on point-to-point and point-to-multipoint networks, not broadcast multi-access. Option C is wrong because 30 seconds is the default hello interval for OSPF on Non-Broadcast Multi-Access (NBMA) networks, such as Frame Relay or ATM, not Ethernet. Option D is wrong because 40 seconds is the default dead interval (not hello interval) on broadcast multi-access networks; the hello interval is 10 seconds.

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MCQmedium

Router R6 has the following OSPF configuration: router ospf 1 router-id 6.6.6.6 network 192.168.0.0 0.0.255.255 area 0 passive-interface default no passive-interface GigabitEthernet0/0 ! interface GigabitEthernet0/0 ip address 192.168.1.6 255.255.255.0 ip ospf 1 area 0 What is the effect of the 'passive-interface default' command?

A.All OSPF interfaces become passive, including GigabitEthernet0/0.

B.Only GigabitEthernet0/0 is active; all other OSPF interfaces are passive.

C.OSPF adjacencies are formed on all interfaces.

D.The 'passive-interface default' command is ignored because the 'network' command is used.

AnswerB

The default passive setting applies to all interfaces except those explicitly set to 'no passive-interface'.

Why this answer

The 'passive-interface default' command sets all OSPF interfaces to passive by default, meaning they will not send or receive OSPF hello packets and thus cannot form adjacencies. The subsequent 'no passive-interface GigabitEthernet0/0' overrides this for that specific interface, making it the only active OSPF interface. This matches option B.

Exam trap

Cisco often tests the interaction between 'passive-interface default' and 'no passive-interface' to see if candidates understand that the default command applies to all interfaces and must be explicitly overridden per interface, rather than assuming the 'network' command alone controls adjacency formation.

How to eliminate wrong answers

Option A is wrong because the 'no passive-interface GigabitEthernet0/0' command explicitly overrides the default passive setting for that interface, so not all interfaces become passive. Option C is wrong because OSPF adjacencies are only formed on interfaces that are not passive; with 'passive-interface default', only GigabitEthernet0/0 is active, so adjacencies form only on that interface. Option D is wrong because the 'passive-interface default' command is not ignored; it works in conjunction with the 'network' command, which defines which interfaces participate in OSPF, but the passive setting controls whether hellos are sent and adjacencies are formed on those interfaces.

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MCQmedium

A network engineer runs the following command on Router R1: R1# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.0.0.2 1 FULL/DR 00:00:32 192.168.1.2 GigabitEthernet0/0 10.0.0.3 1 2WAY/DROTHER 00:00:35 192.168.1.3 GigabitEthernet0/0 Based on this output, what can be concluded?

A.R1 is the Backup Designated Router (BDR) on this segment.

B.R1 has a full OSPF adjacency with the neighbor 10.0.0.3.

C.R1 is a DROTHER on this segment.

D.The OSPF network type is point-to-point.

AnswerC

Since the DR is 10.0.0.2 and the BDR is not listed, and R1 has a full adjacency only with the DR, R1 must be a DROTHER.

Why this answer

The output shows R1 has a neighbor with state 2WAY/DROTHER (10.0.0.3), which indicates that R1 is also a DROTHER on this broadcast multiaccess segment. The FULL/DR neighbor (10.0.0.2) is the Designated Router, and since R1 is not the BDR (no FULL/BDR state), it must be a DROTHER.

Exam trap

Cisco often tests the misconception that 2WAY state means a full adjacency, but in OSPF, 2WAY is a normal neighbor state on broadcast networks between DROTHERs, not a full adjacency (which requires FULL state).

How to eliminate wrong answers

Option A is wrong because R1 is not the BDR; the BDR would appear with state FULL/BDR, but the only FULL neighbor is the DR (10.0.0.2). Option B is wrong because the neighbor 10.0.0.3 is in the 2WAY state, not FULL, meaning they have an established neighbor relationship but not a full adjacency (they exchange Hellos but not LSAs directly). Option D is wrong because the presence of DR/BDR states (FULL/DR, 2WAY/DROTHER) indicates a broadcast multiaccess network type, not point-to-point.

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Multi-Selecthard

Which three statements about OSPF LSA types are correct? (Choose three.)

Select 3 answers

A.Type 1 LSAs (Router LSAs) are generated by every OSPF router and describe the router's interfaces and neighbors within an area.

B.Type 2 LSAs (Network LSAs) are generated by the DR on broadcast and NBMA networks to list all routers attached to the segment.

C.Type 3 LSAs (Summary LSAs) are generated by ASBRs to advertise external routes into the OSPF domain.

D.Type 4 LSAs (ASBR Summary LSAs) are generated by ABRs to advertise the location of an ASBR to routers in other areas.

E.Type 5 LSAs (AS External LSAs) are flooded only within the area where they originate.

AnswersA, B, D

Correct because Router LSAs are the fundamental LSA type, created by each router to advertise its directly connected links and state.

Why this answer

OSPF uses various LSA types to describe different routing information. Type 1 (Router LSA) is generated by every router. Type 2 (Network LSA) is generated by the DR.

Type 3 (Summary LSA) is generated by ABRs. Type 4 (ASBR Summary LSA) is also generated by ABRs. Type 5 (AS External LSA) originates from ASBRs and is flooded throughout the entire OSPF domain.

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Drag & Dropmedium

Drag and drop the steps of OSPF redistribution from EIGRP with metric conversion into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

First, identify the EIGRP routes to redistribute into OSPF. Then, configure the OSPF redistribution command under the OSPF process, specifying the EIGRP AS number. Since OSPF requires a metric for redistributed routes, set the OSPF metric type (E1 or E2) and seed metric.

Optionally, use a route map to filter or modify specific routes. Finally, verify that the redistributed routes appear in the OSPF database and routing table.

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Drag & Dropmedium

Drag and drop the steps of OSPF summarization at ABR configuration steps into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

First, identify the subnets to summarize into a single prefix. Then, configure the area range command on the ABR under the OSPF process, specifying the area and the summary prefix. Optionally, set the 'not-advertise' keyword to suppress the summary.

Verify the summary route in the OSPF database using 'show ip ospf summary-address'. Finally, check that the summary route appears in the routing table of other routers.

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Drag & Drophard

Drag and drop the steps of OSPF redistribution from EIGRP with metric conversion into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

Redistribution requires enabling redistribution, setting a seed metric (or using default-metric), optionally matching routes, and then verifying. The order ensures routes are properly injected.

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Matchingmedium

Drag and drop each OSPF packet type on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Discovers and maintains OSPF neighbor adjacencies

Contains a summary of the link-state database for initial synchronization

Requests specific link-state advertisements from a neighbor

Carries one or more full LSAs during flooding or in response to an LSR

Acknowledges receipt of an LSU to ensure reliable flooding

Why these pairings

Hello packets discover and maintain neighbor relationships. DBD (Database Description) packets contain a summary of the LSDB for synchronization. LSR (Link-State Request) packets request specific LSAs.

LSU (Link-State Update) packets carry full LSAs in response to LSRs or during flooding. LSAck (Link-State Acknowledgment) packets confirm receipt of LSUs.

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Drag & Drophard

Drag and drop the steps of OSPF route redistribution into a different autonomous system into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

Redistribution requires first configuring the routing process that will receive the routes, then defining the source protocol and metric, optionally setting route tags for loop prevention, applying a route map for filtering, and finally verifying the redistributed routes appear in the OSPF database.

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Drag & Dropmedium

Drag and drop the steps of OSPFv3 IPv6 neighbor adjacency formation into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

OSPFv3 neighbor formation begins with the router sending Hello packets on the link. The neighbor receives the Hello and replies with its own Hello, including the router ID. Both routers then exchange Database Description packets to summarize their LSDB.

Link State Request packets are sent for missing LSAs, and Link State Update packets provide the requested LSAs. Finally, Link State Acknowledgment packets confirm receipt, completing the adjacency.

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MCQeasy

What is the default OSPF reference bandwidth used for cost calculation in Cisco IOS?

A.100 Mbps

B.1000 Mbps

C.10 Mbps

D.1 Mbps

AnswerA

The default reference bandwidth is 100 Mbps, as defined in the OSPF specification.

Why this answer

In Cisco IOS, the default OSPF reference bandwidth is 100 Mbps. OSPF calculates the cost of an interface as the reference bandwidth divided by the interface bandwidth. With the default reference of 100 Mbps, a FastEthernet (100 Mbps) interface gets a cost of 1, which is the minimum cost.

This default was established when FastEthernet was considered high-speed, but it can be changed using the 'auto-cost reference-bandwidth' command to accommodate faster links like GigabitEthernet.

Exam trap

Cisco often tests the default OSPF reference bandwidth as 100 Mbps, and the trap here is that candidates confuse it with the actual interface bandwidth (e.g., 10 Mbps for Ethernet) or assume it matches the fastest common link speed (e.g., 1000 Mbps for GigabitEthernet).

How to eliminate wrong answers

Option B (1000 Mbps) is wrong because 1000 Mbps is not the default; it is a common value set manually to avoid cost rounding issues on GigabitEthernet and faster interfaces. Option C (10 Mbps) is wrong because 10 Mbps is the bandwidth of an Ethernet interface, not the reference bandwidth; using 10 Mbps would make all faster links have fractional costs. Option D (1 Mbps) is wrong because 1 Mbps is the bandwidth of a legacy serial link and would result in extremely high costs for modern interfaces; the default reference bandwidth is 100 Mbps.

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MCQmedium

A network engineer is troubleshooting OSPF adjacency issues between two routers connected via a Gigabit Ethernet link. The engineer notices that the routers are stuck in the EXSTART state. Both routers have the same MTU of 1500 bytes. What is the most likely cause of this issue?

A.The OSPF network type is point-to-point on one router and broadcast on the other.

B.The OSPF hello and dead intervals are mismatched.

C.One router has a lower IP MTU configured on the interface, causing the DBD packet to be dropped.

D.The OSPF router IDs are the same.

AnswerC

Correct because OSPF routers exchange DBD packets in the EXSTART state. If the DBD packet size exceeds the IP MTU, the packet is dropped, and the routers remain stuck in EXSTART.

Why this answer

When OSPF routers are stuck in the EXSTART state, it typically indicates a problem with the Database Description (DBD) packet exchange. Even though both routers have the same configured MTU of 1500 bytes, one router may have a lower IP MTU on its interface (e.g., due to a different interface MTU or encapsulation overhead), causing the DBD packet to be fragmented or dropped. Since OSPF DBD packets are not fragmented, a mismatch in the actual IP MTU prevents the adjacency from progressing beyond EXSTART.

Exam trap

Cisco often tests the nuance that the configured MTU (e.g., 1500 bytes) may not equal the actual IP MTU due to overhead from encapsulation or interface settings, leading to DBD packet drops and a stuck EXSTART state.

How to eliminate wrong answers

Option A is wrong because mismatched OSPF network types (e.g., point-to-point vs. broadcast) would cause the routers to get stuck in the INIT or 2-WAY state, not EXSTART; the DBD exchange process is not even reached. Option B is wrong because mismatched hello and dead intervals prevent the routers from forming a neighbor relationship at all, leaving them stuck in the DOWN or INIT state, not EXSTART. Option D is wrong because duplicate OSPF router IDs would cause a conflict that prevents adjacency formation, typically resulting in a state of DOWN or INIT, not EXSTART.

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MCQmedium

An enterprise network uses OSPF as its IGP. The network engineer notices that a particular route learned via OSPF is not being installed in the routing table, even though the neighbor adjacency is up and the route appears in the OSPF database. The route is an external route redistributed from EIGRP. What is the most likely cause?

A.The OSPF process ID is different on the routers.

B.The external route has a higher administrative distance than the internal route.

C.The forwarding address in the type 5 LSA is not reachable via an OSPF internal route.

D.The OSPF metric for the external route is too high.

AnswerC

Correct because OSPF requires the forwarding address to be reachable via an intra-area or inter-area route; otherwise, the external route is not installed.

Why this answer

Option C is correct because OSPF requires the forwarding address (FA) in a Type 5 LSA to be reachable via an OSPF internal route (intra-area or inter-area) for the external route to be installed in the routing table. If the FA is not reachable, the router will ignore the LSA and not install the route, even though the LSA exists in the OSPF database and the neighbor adjacency is up.

Exam trap

Cisco often tests the forwarding address reachability requirement for Type 5 LSAs, and the trap here is that candidates assume any route in the OSPF database will automatically be installed, ignoring the recursive lookup condition for external routes with a non-zero forwarding address.

How to eliminate wrong answers

Option A is wrong because the OSPF process ID is locally significant and does not affect route installation between routers; different process IDs can still form adjacencies and exchange routes. Option B is wrong because OSPF external routes (type 5) have a default administrative distance of 110, while internal OSPF routes also have 110; the issue is not about AD comparison between internal and external OSPF routes, but about reachability of the forwarding address. Option D is wrong because a high OSPF metric does not prevent route installation; it only influences route selection among multiple paths; the route will still be installed if the metric is valid and the forwarding address is reachable.

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MCQmedium

A network engineer runs the following command on Router R9: R9# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Gi0/0 1 0 192.168.1.9/24 10 DR 2/2 Gi0/1 1 1 10.0.0.9/24 20 BDR 1/1 Lo0 1 0 9.9.9.9/32 1 LOOP 0/0 Based on this output, what can be concluded?

A.R9 is the Designated Router on the segment connected to Gi0/1.

B.R9 has two fully adjacent neighbors on Gi0/0.

C.The loopback interface Lo0 is advertised as a /24 network.

D.R9 is an Area Border Router.

AnswerB

The Nbrs F/C column shows 2/2, meaning 2 neighbors and 2 full adjacencies.

Why this answer

The output shows that on interface Gi0/0, R9 has a state of DR (Designated Router) and 2 fully adjacent neighbors (Nbrs F/C = 2/2). The '2/2' indicates 2 neighbors in a full state out of 2 total neighbors, meaning both neighbors have completed the OSPF adjacency process. Therefore, R9 has two fully adjacent neighbors on Gi0/0, making option B correct.

Exam trap

Cisco often tests the misinterpretation of the 'Nbrs F/C' field, where candidates confuse the total neighbor count with the number of fully adjacent neighbors, or assume that being in the DR state on one interface implies DR status on all interfaces.

How to eliminate wrong answers

Option A is wrong because on Gi0/1, R9 is in the BDR (Backup Designated Router) state, not DR; the DR on that segment would be another router. Option C is wrong because the loopback interface Lo0 is configured with a /32 mask (as shown by 9.9.9.9/32), and OSPF advertises it as a host route (/32) by default, not as a /24 network. Option D is wrong because R9 has interfaces in Area 0 and Area 1, but the output does not show any interface in a different area that would indicate it is an ABR; an ABR must have at least one interface in Area 0 and one in another non-backbone area, which is true here, but the output does not confirm that R9 is actually performing ABR functions (e.g., it could be a simple multi-area router without LSA type 3 generation), and the question asks what can be concluded from the output—being in two areas does not automatically mean it is an ABR without further evidence of route redistribution between areas.

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MCQhard

A network engineer issues the following command on Router R6: R6# debug ip ospf hello OSPF: Send hello to 224.0.0.5 via GigabitEthernet0/0 (192.168.1.6) OSPF: Rcv hello from 1.1.1.1, GigabitEthernet0/0, area 0.0.0.0 Neighbor state is 2WAY, options 0x2 OSPF: End of hello processing Based on this output, what can be concluded?

A.R6 has formed a full adjacency with neighbor 1.1.1.1.

B.The hello packet was sent to the DR/BDR multicast address 224.0.0.6.

C.R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.

D.The OSPF network type is point-to-point.

AnswerC

2WAY is a valid neighbor state indicating two-way communication, but full adjacency requires further exchange (e.g., on broadcast networks, only with DR/BDR).

Why this answer

The debug output shows the neighbor state is 2WAY, which indicates that R6 has received a hello from 1.1.1.1 and bidirectional communication is established, but a full adjacency has not yet been formed. In OSPF, the 2WAY state is a prerequisite for advancing to the ExStart state and eventually to FULL, but on multiaccess networks, the router must also wait for the Designated Router (DR) and Backup Designated Router (BDR) election process to complete before proceeding. Therefore, option C correctly states that R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.

Exam trap

Cisco often tests the distinction between the 2WAY and FULL states, and the trap here is that candidates mistakenly assume that receiving a hello packet means a full adjacency has been formed, ignoring the multi-step OSPF neighbor state machine and the role of DR/BDR elections on broadcast networks.

How to eliminate wrong answers

Option A is wrong because the neighbor state is 2WAY, not FULL; a full adjacency is only achieved after the database description (DBD), LSR, LSU, and LSAck exchanges in the ExStart, Exchange, Loading, and FULL states. Option B is wrong because the hello packet was sent to 224.0.0.5, which is the AllSPFRouters multicast address used for OSPF hello packets on broadcast and point-to-point networks, not the DR/BDR multicast address 224.0.0.6. Option D is wrong because the use of multicast address 224.0.0.5 and the presence of a 2WAY state (which implies a DR/BDR election process) strongly suggest a broadcast network type, not point-to-point; on a point-to-point link, neighbors typically transition directly to FULL without a 2WAY state.

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Multi-Selecteasy

Which two statements about OSPF neighbor states are true? (Choose two.)

Select 2 answers

A.The 2-Way state indicates that both routers have seen their own router ID in the neighbor's hello packet.

B.The Full state indicates that the routers have synchronized their LSDBs and are fully adjacent.

C.In the ExStart state, routers exchange Database Description packets containing LSA headers.

D.In the Exchange state, routers send Link State Requests and receive Link State Updates.

E.The Down state is the final state when a neighbor is unreachable.

AnswersA, B

Correct because 2-Way confirms bidirectional communication, which is required before proceeding to database synchronization.

Why this answer

Option A is correct because the 2-Way state indicates that both routers have received each other's hello packets, confirming bidirectional communication. Option B is correct because the Full state means that the routers have exchanged all LSAs and their databases are synchronized. Option C is incorrect because the ExStart state is where the master/slave relationship is established, not where LSAs are exchanged.

Option D is incorrect because the Loading state is where LSRs and LSUs are exchanged, not the Exchange state. Option E is incorrect because the Down state is the initial state before any hello packets are received.

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MCQmedium

A network engineer is configuring OSPF in a multi-area design. The engineer wants to reduce the amount of LSA flooding and the size of the LSDB in area 0. Which OSPF feature should be implemented on the ABR to achieve this goal?

A.Configure area 0 as a stub area.

B.Configure the ABR with an area filter-list to filter type 3 LSAs.

C.Configure OSPF database overflow protection.

D.Configure the ABR as an ASBR.

AnswerB

Correct because area filter-list can be used on an ABR to filter type 3 LSAs between areas, reducing LSDB size in area 0.

Why this answer

Option B is correct because configuring an area filter-list on the ABR allows the engineer to filter Type 3 summary LSAs entering or leaving area 0. This directly reduces LSA flooding and shrinks the LSDB in area 0 by preventing specific inter-area prefixes from being advertised into the backbone, without altering the area type or requiring additional redistribution.

Exam trap

The trap here is that candidates often assume area 0 can be made a stub area to reduce LSAs, but Cisco tests the fact that area 0 is a transit area and cannot be a stub, making the filter-list the correct tool for this specific goal.

How to eliminate wrong answers

Option A is wrong because area 0 cannot be configured as a stub area; OSPF requires area 0 to be a transit area and stub areas cannot have virtual links or ASBRs, making this configuration invalid. Option C is wrong because OSPF database overflow protection limits the total number of LSAs in the LSDB to prevent memory exhaustion, but it does not selectively reduce LSA flooding or the LSDB size in area 0 as requested. Option D is wrong because configuring the ABR as an ASBR would introduce external LSAs (Type 5) into the OSPF domain, increasing the LSDB size and flooding, which is the opposite of the goal.

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MCQmedium

A network engineer issues the following command on Router R8: R8# show ip ospf neighbor detail Neighbor 1.1.1.1, interface address 192.168.1.1 In the area 0 via interface GigabitEthernet0/0 Neighbor priority is 1, State is FULL, 6 state changes DR is 192.168.1.2, BDR is 192.168.1.1 Options is 0x42 (L LSR LSRR L LSR) Dead timer due in 00:00:34 Neighbor is up for 00:12:45 Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0) Last retransmission scan length is 0, last retransmission scan time is 0 msec Based on this output, what can be concluded?

A.Router 1.1.1.1 is the Designated Router on this segment.

B.Router 1.1.1.1 is the Backup Designated Router.

C.The neighbor state is 2WAY.

D.The dead timer is 40 seconds.

AnswerB

The BDR is 192.168.1.1, which is the interface address of neighbor 1.1.1.1.

Why this answer

The output shows 'BDR is 192.168.1.1', which is the interface address of neighbor 1.1.1.1. This directly indicates that router 1.1.1.1 is the Backup Designated Router on this segment. The neighbor state is FULL, confirming adjacency is fully established.

Exam trap

Cisco often tests the distinction between the neighbor's Router ID (1.1.1.1) and its interface address (192.168.1.1), causing candidates to confuse which router is the DR or BDR based on the Router ID rather than the explicit DR/BDR fields.

How to eliminate wrong answers

Option A is wrong because the DR is 192.168.1.2, not 1.1.1.1; the neighbor's interface address is 192.168.1.1, which is the BDR. Option C is wrong because the neighbor state is explicitly shown as 'FULL', not 2WAY; 2WAY is a lower state before adjacency formation. Option D is wrong because the dead timer is shown as 00:00:34, which is 34 seconds remaining, not 40 seconds; the default dead interval is 40 seconds, but the timer counts down.

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Drag & Dropmedium

Drag and drop the steps of OSPF neighbor adjacency formation into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

OSPF neighbors transition through Down, Init, 2-Way, ExStart, Exchange, Loading, and Full states. The correct order begins with the router sending Hello packets (Down to Init), then receiving a Hello reply (Init to 2-Way), electing DR/BDR if needed (2-Way to ExStart), exchanging database description packets (ExStart to Exchange), and finally synchronizing databases (Loading to Full).

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MCQmedium

A network engineer is configuring OSPF on a router that connects to two different ISPs. The engineer wants to prefer one ISP for all external routes unless that ISP's link fails, in which case the other ISP should be used. Which OSPF feature should be used to influence the path selection for external routes?

A.Configure the OSPF cost on the interface connecting to the preferred ISP to a lower value.

B.Use the 'distance ospf external' command to set a higher administrative distance for external routes from the less preferred ISP.

C.Use the 'max-metric' command on the router connecting to the less preferred ISP.

D.Configure the OSPF network type to point-to-point on both interfaces.

AnswerB

Correct because by setting a higher administrative distance for external routes from one ISP, the router will prefer routes with lower administrative distance from the other ISP.

Why this answer

Option B is correct because the 'distance ospf external' command allows you to set a higher administrative distance for external OSPF routes learned from a specific neighbor or source, making the routes from the less preferred ISP less trustworthy. When the preferred ISP's link fails, those routes are removed, and the router will then use the external routes from the backup ISP due to their lower administrative distance (or default distance if not changed). This directly influences path selection for external routes without altering OSPF metrics or interface costs.

Exam trap

The trap here is that candidates often confuse OSPF cost (metric) with administrative distance, thinking that lowering the interface cost will make external routes from that ISP preferred, but OSPF cost only affects internal path selection, not the preference between different routing sources for external routes.

How to eliminate wrong answers

Option A is wrong because OSPF cost influences intra-area and inter-area route selection, but external routes (type 5 or 7 LSAs) are selected based on the forwarding address and metric type (E1/E2); changing interface cost does not directly control preference between two ISPs for external routes. Option C is wrong because the 'max-metric' command sets the router's own link-state metrics to a high value (like 65535) to avoid being a transit router, but it does not influence the selection of external routes learned from different ISPs. Option D is wrong because configuring the OSPF network type to point-to-point affects neighbor discovery and LSA flooding behavior, not the administrative distance or preference for external routes.

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Drag & Dropmedium

Drag and drop the steps of OSPF virtual link configuration across area 0 into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

First, ensure the transit area (non-backbone) has full connectivity and at least one ABR. Then, identify the router IDs of the two ABRs that will form the virtual link. On each ABR, configure the virtual link using the 'area transit-area-id virtual-link router-id' command.

Verify the virtual link state using 'show ip ospf virtual-links'. Finally, confirm that routes from the backbone area are now reachable across the virtual link.

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Multi-Selectmedium

Which two statements about OSPF neighbor states are true? (Choose two.)

Select 2 answers

A.The 2-Way state indicates that the router has received a Hello packet from the neighbor with its own Router ID in the neighbor list.

B.In the ExStart state, routers exchange Database Description (DBD) packets to describe their LSDB contents.

C.The Full state means the routers have synchronized their link-state databases and are fully adjacent.

D.The Loading state occurs before the Exchange state in the neighbor state machine.

E.The Down state means the router has received a Hello packet from the neighbor but has not yet established two-way communication.

AnswersA, C

Correct because 2-Way state confirms bidirectional communication: each router sees its own Router ID in the other's Hello packet.

Why this answer

OSPF neighbor state machine progresses through several states. The 2-Way state indicates bidirectional communication has been established. The Full state means the routers have exchanged complete LSDB information.

The ExStart state is where the master/slave relationship is determined. The Loading state occurs after the Database Description (DBD) exchange.

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MCQmedium

Consider the following OSPF configuration on router R2: interface GigabitEthernet0/0 ip address 192.168.1.2 255.255.255.0 ip ospf 1 area 0 ip ospf hello-interval 5 ! router ospf 1 router-id 2.2.2.2 network 192.168.1.0 0.0.0.255 area 0 Which statement is true about this configuration?

A.The OSPF dead interval is automatically set to 20 seconds.

B.The OSPF dead interval remains at the default of 40 seconds.

C.This configuration will cause OSPF to use MD5 authentication.

D.The OSPF network type changes to point-to-point.

AnswerA

By default, the dead interval is 4 times the hello interval, so with hello 5, dead becomes 20 seconds.

Why this answer

The correct answer is A because the OSPF dead interval is automatically set to four times the hello interval when the hello interval is manually configured. By default, OSPF uses a hello interval of 10 seconds and a dead interval of 40 seconds on broadcast networks. However, when you explicitly set the hello interval to 5 seconds using the 'ip ospf hello-interval 5' command, the router automatically adjusts the dead interval to 20 seconds (4 × 5 seconds) to maintain the standard ratio, unless the dead interval is also manually configured.

Exam trap

Cisco often tests the automatic relationship between the OSPF hello and dead intervals, and the trap here is that candidates assume the dead interval remains at the default value (40 seconds) even after changing the hello interval, rather than understanding it scales proportionally to 4× the new hello interval.

How to eliminate wrong answers

Option B is wrong because the OSPF dead interval does not remain at the default of 40 seconds; it is automatically recalculated to 20 seconds when the hello interval is changed to 5 seconds. Option C is wrong because the configuration shown does not include any authentication commands such as 'ip ospf authentication message-digest' or 'ip ospf message-digest-key', so MD5 authentication is not enabled. Option D is wrong because the network type remains as the default broadcast (multi-access) for GigabitEthernet interfaces; changing the network type to point-to-point requires the explicit command 'ip ospf network point-to-point'.

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Matchingmedium

Drag and drop each OSPF router role on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Generates the Network LSA and maintains full adjacencies with all routers on the segment

Monitors the DR and assumes the DR role if the DR fails

Forms full adjacencies only with the DR and BDR

Connects multiple areas and advertises inter-area routes

Redistributes external routes into OSPF

Why these pairings

The DR (Designated Router) generates the Network LSA and manages LSDB synchronization on multiaccess networks. The BDR (Backup Designated Router) monitors the DR and takes over if the DR fails. DROTHERs form full adjacencies only with the DR and BDR, not with each other.

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Matchingmedium

Drag and drop each OSPF network type on the left to its matching DR election behavior on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Elects DR and BDR; uses multicast Hello to 224.0.0.5

Elects DR and BDR; uses unicast Hello to configured neighbors

No DR/BDR election; uses multicast 224.0.0.5

Always advertised as a /32 host route; no DR election

Why these pairings

Broadcast network type elects DR/BDR and uses multicast 224.0.0.5/6; Non-broadcast (NBMA) also elects DR/BDR but uses unicast; Point-to-point does not elect DR/BDR; Point-to-multipoint does not elect DR/BDR and uses multicast; Loopback interface is always advertised as a /32 host route regardless of configured mask.

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MCQmedium

A network engineer runs the following command on Router R5: R5# show ip ospf border-routers OSPF Process 1 internal Routing Table Codes: i - Intra-area route, I - Inter-area route i 1.1.1.1 [110/10] via 192.168.1.1, GigabitEthernet0/0, ABR, Area 0, SPF 5 i 2.2.2.2 [110/20] via 192.168.1.2, GigabitEthernet0/0, ASBR, Area 0, SPF 5 Based on this output, what can be concluded?

A.Router 1.1.1.1 connects area 0 to another OSPF area.

B.Router 2.2.2.2 is an Area Border Router.

C.Router 1.1.1.1 is redistributing external routes into OSPF.

D.The route to 2.2.2.2 is an inter-area route.

AnswerA

ABR indicates it connects multiple areas.

Why this answer

The output shows an entry for 1.1.1.1 with the label 'ABR' (Area Border Router) and a route type of 'i' (intra-area). An ABR connects two or more OSPF areas, so Router 1.1.1.1 must be connecting Area 0 to another OSPF area. The metric [110/10] and next-hop 192.168.1.1 confirm it is reachable within Area 0.

Exam trap

Cisco often tests the distinction between ABR and ASBR roles in the 'show ip ospf border-routers' output, where candidates mistakenly assume any border router is an ABR or confuse the 'i' and 'I' route codes.

How to eliminate wrong answers

Option B is wrong because the output explicitly labels 2.2.2.2 as 'ASBR' (Autonomous System Boundary Router), not ABR; an ASBR redistributes external routes into OSPF, it does not connect areas. Option C is wrong because 1.1.1.1 is labeled 'ABR', not 'ASBR'; only an ASBR redistributes external routes into OSPF. Option D is wrong because the route to 2.2.2.2 is marked with 'i' (intra-area), not 'I' (inter-area); inter-area routes are denoted by a capital 'I' in the OSPF routing table.

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Multi-Selectmedium

Which two statements about OSPF network types are true? (Choose two.)

Select 2 answers

A.The point-to-point network type does not require a DR/BDR election.

B.The broadcast network type uses a DR/BDR to reduce the number of adjacencies.

C.The NBMA network type automatically discovers neighbors via hello packets.

D.The point-to-multipoint network type requires a DR/BDR election.

E.The loopback interface defaults to the point-to-point network type.

AnswersA, B

Correct because in point-to-point networks, there are only two routers, so no DR/BDR is needed.

Why this answer

Option A is correct because the point-to-point network type does not require a DR/BDR election. Option B is correct because the broadcast network type uses a DR/BDR to reduce adjacencies and LSAs. Option C is incorrect because NBMA networks require manual neighbor configuration.

Option D is incorrect because the point-to-multipoint network type does not require a DR/BDR. Option E is incorrect because the loopback interface defaults to the loopback network type, not point-to-point.

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Multi-Selecthard

Which three statements about OSPF area types are correct? (Choose three.)

Select 3 answers

A.A stub area blocks Type 5 AS External LSAs but allows Type 3 Summary LSAs and a default route.

B.A totally stubby area blocks both Type 5 and Type 3 LSAs, injecting only a default route into the area.

C.A not-so-stubby-area (NSSA) allows Type 5 LSAs to be imported from external networks.

D.A standard area can contain Type 1, 2, 3, 4, and 5 LSAs.

E.A totally NSSA blocks Type 3 LSAs but allows Type 5 LSAs from external sources.

AnswersA, B, D

Correct because stub areas are designed to reduce the LSDB by preventing Type 5 LSAs, while still receiving inter-area routes via Type 3 and a default route.

Why this answer

OSPF area types control the propagation of LSAs. A standard area can carry all LSA types. A stub area blocks Type 5 LSAs but allows Type 3.

A totally stubby area blocks both Type 5 and Type 3 (except a default route). A not-so-stubby-area (NSSA) blocks Type 5 but allows Type 7 for external routes. A totally NSSA further blocks Type 3.

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Matchingmedium

Drag and drop each OSPF LSA type on the left to its matching description on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Describes a router's directly attached links and interfaces

Generated by the DR to list all routers on a multiaccess segment

Advertises inter-area prefixes between areas

Advertises the location of an ASBR to other areas

Advertises external routes redistributed into OSPF

Why these pairings

LSA Type 1 (Router LSA) describes a router's own interfaces and links. Type 2 (Network LSA) is generated by the DR to describe all routers on a multiaccess network. Type 3 (Summary LSA) advertises networks from one area to another.

Type 4 (ASBR Summary LSA) advertises the location of an ASBR. Type 5 (AS External LSA) advertises external routes redistributed into OSPF.

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Drag & Dropmedium

Drag and drop the steps of OSPFv3 IPv6 neighbor adjacency formation into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

OSPFv3 neighbor formation follows the same state machine as OSPFv2: Down, Init, 2-Way, ExStart, Exchange, Loading, Full. The steps reflect the key actions at each state.

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Matchingmedium

Drag and drop each OSPF router role on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Generates Type 2 Network LSA and maintains full adjacencies with all routers on the segment

Becomes DR if the current DR fails; also maintains full adjacencies

Forms adjacencies only with DR and BDR; does not form full adjacencies with other DROTHERs

Redistributes routes from other routing protocols into OSPF

Connects two or more OSPF areas and advertises inter-area routes

Why these pairings

DR (Designated Router) generates Network LSAs and manages adjacencies on multi-access networks; BDR (Backup DR) takes over if the DR fails; DROTHER routers form full adjacencies only with DR and BDR; ASBR redistributes routes from other protocols; ABR connects multiple areas.

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Drag & Dropmedium

Drag and drop the steps of OSPF SPF calculation steps (Dijkstra) into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

The Dijkstra SPF algorithm first initializes the candidate list with the root router itself. It then examines the root's neighbors, adding them to the candidate list. The router with the lowest cost is moved from candidate to the SPF tree.

The process repeats by examining the newly added router's neighbors and updating the candidate list. Finally, when all routers are in the SPF tree, the algorithm terminates and the routing table is populated.

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MCQhard

A network engineer issues the following command on Router R4: R4# show ip ospf database OSPF Router with ID (4.4.4.4) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 123 0x80000002 0x00A1B2 2 2.2.2.2 2.2.2.2 456 0x80000003 0x00B2C3 3 4.4.4.4 4.4.4.4 789 0x80000001 0x00C3D4 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.1.2 2.2.2.2 234 0x80000001 0x00D4E5 Based on this output, what can be concluded?

A.Router 2.2.2.2 is the Designated Router on the segment 192.168.1.0/24.

B.Router 1.1.1.1 has three OSPF-enabled interfaces.

C.Router 4.4.4.4 is the BDR on the segment.

D.There are multiple broadcast segments in area 0.

AnswerA

The Net Link State is originated by the DR, and the ADV Router is 2.2.2.2, so it is the DR.

Why this answer

The Net Link States entry shows the link ID 192.168.1.2 (the DR's interface IP) and ADV Router 2.2.2.2, which indicates that router 2.2.2.2 is the Designated Router (DR) on the 192.168.1.0/24 segment. In OSPF, only the DR originates the Type 2 (Network LSA) for a broadcast segment, so the advertising router in the Net Link States is always the DR.

Exam trap

Cisco often tests the misconception that the ADV Router in a Net Link State is the router that owns the IP address in the Link ID field, when in fact it is always the DR on that segment.

How to eliminate wrong answers

Option B is wrong because the Router Link States show a link count of 2 for router 1.1.1.1, meaning it has exactly two OSPF-enabled interfaces, not three. Option C is wrong because the output does not include any information about the BDR; the Net Link States only identifies the DR (2.2.2.2), and there is no separate BDR field in the OSPF database output. Option D is wrong because only one Net Link State entry is present (for 192.168.1.0/24), which indicates a single broadcast segment in area 0; multiple broadcast segments would produce multiple Type 2 LSAs.

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MCQmedium

Router R1 has the following OSPF configuration: interface GigabitEthernet0/0 ip address 10.1.1.1 255.255.255.0 ip ospf 1 area 0 ip ospf network point-to-point ! router ospf 1 router-id 1.1.1.1 network 10.0.0.0 0.255.255.255 area 0 What is the effect of the 'ip ospf network point-to-point' command on this interface?

A.It disables OSPF on the interface.

B.It changes the OSPF network type to point-to-point, eliminating DR/BDR election and reducing hello timer to 10 seconds.

C.It enables OSPF authentication on the interface.

D.It sets the OSPF cost to 1.

AnswerB

Point-to-point network type removes DR/BDR election and uses 10-second hello and 40-second dead timers.

Why this answer

The 'ip ospf network point-to-point' command changes the OSPF network type on the interface from the default (broadcast for Ethernet) to point-to-point. This eliminates the need for a Designated Router (DR) and Backup Designated Router (BDR) election, as point-to-point links have only two neighbors. Additionally, the OSPF hello timer on a point-to-point network defaults to 10 seconds (versus 30 seconds for non-broadcast), and the dead timer is 40 seconds.

Exam trap

Cisco often tests the misconception that 'ip ospf network point-to-point' disables OSPF or changes timers to 30 seconds, when in fact it eliminates DR/BDR and sets hello to 10 seconds.

How to eliminate wrong answers

Option A is wrong because the command does not disable OSPF; it modifies the network type while OSPF remains active. Option C is wrong because OSPF authentication is configured separately using 'ip ospf authentication' or 'ip ospf authentication-key' commands, not by changing the network type. Option D is wrong because the OSPF cost is not set to 1 by this command; cost is derived from interface bandwidth (default 100 Mbps / bandwidth) or manually set with 'ip ospf cost'.

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Drag & Dropmedium

Drag and drop the steps of OSPF summarization at ABR configuration steps into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

Summarization on an ABR uses the area range command to aggregate prefixes. The order is: identify prefixes, configure range, verify, and optionally suppress more specific routes.

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Multi-Selectmedium

Which two statements about OSPF network types are true? (Choose two.)

Select 2 answers

A.On a broadcast multiaccess network, OSPF elects a DR and BDR to reduce LSA flooding.

B.The OSPF point-to-point network type requires a DR/BDR election.

C.On a non-broadcast multiaccess (NBMA) network, OSPF can use the neighbor command to manually discover neighbors.

D.The OSPF point-to-multipoint network type always elects a DR.

E.The default OSPF network type for a loopback interface is point-to-point.

AnswersA, C

Correct because on broadcast networks (e.g., Ethernet), a Designated Router (DR) and Backup DR are elected to minimize the number of adjacencies and flooding.

Why this answer

OSPF network types control how adjacencies are formed and how LSAs are flooded. Broadcast and non-broadcast types require a DR/BDR election, while point-to-point and point-to-multipoint do not. The loopback interface defaults to loopback network type, not point-to-point.

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MCQeasy

A network engineer is designing an OSPF network with multiple areas. The engineer wants to ensure that routers in area 2 can reach networks in area 0, but they should not learn any external routes from other ASs. Which OSPF area type should be configured for area 2?

A.Stub area

B.Not-so-stubby area (NSSA)

C.Totally stubby area

D.Standard area

AnswerA

Correct because a stub area blocks type 5 LSAs, preventing external routes from being learned, and uses a default route for external destinations.

Why this answer

A stub area blocks Type 5 LSAs (external routes from other ASs) while allowing Type 3 summary LSAs from area 0. This ensures routers in area 2 can reach networks in area 0 via inter-area routes but do not learn external routes, meeting the requirement exactly.

Exam trap

Cisco often tests the distinction between stub and totally stubby areas: candidates confuse 'blocking external routes' with 'blocking all routes except the default,' forgetting that a stub area still allows inter-area summary LSAs (Type 3) from area 0.

How to eliminate wrong answers

Option B (NSSA) is wrong because it allows Type 7 LSAs to carry external routes into the area, which would still introduce external routes from other ASs, violating the requirement. Option C (totally stubby area) is wrong because it blocks both Type 5 and Type 3 LSAs, preventing routers in area 2 from learning inter-area routes to networks in area 0. Option D (standard area) is wrong because it permits all LSA types, including Type 5 external LSAs, so routers would learn external routes from other ASs.

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MCQeasy

A network engineer is configuring OSPF on a router that has multiple interfaces in the same area. The engineer wants to ensure that the router does not become the designated router (DR) on any of these interfaces. What should the engineer do?

A.Set the OSPF priority to 0 on all interfaces.

B.Configure the OSPF network type as point-to-point on all interfaces.

C.Use the 'ip ospf dr-priority' command to set a high priority on other routers.

D.Configure the router as an ABR.

AnswerA

Correct because a priority of 0 means the router will not be elected as DR or BDR.

Why this answer

Setting the OSPF priority to 0 on all interfaces prevents the router from participating in the DR/BDR election process. A router with priority 0 will never become the DR or BDR on any segment, regardless of its Router ID or other factors. This is the only method that guarantees the router will not be elected as DR on any interface.

Exam trap

The trap here is that candidates often confuse DR/BDR election prevention with network type changes, thinking that point-to-point is the only way to avoid DR election, but the priority 0 method is the direct and correct answer for preventing a specific router from becoming DR without altering the network type.

How to eliminate wrong answers

Option B is wrong because configuring the OSPF network type as point-to-point eliminates the need for a DR/BDR election entirely, but it does not prevent the router from becoming the DR on interfaces that are not point-to-point; it changes the election behavior on those specific interfaces, but the question asks for a solution that works on all interfaces without altering the network type. Option C is wrong because setting a high priority on other routers does not guarantee that this router will not become the DR; if those other routers are not present or have lower Router IDs, this router could still be elected. Option D is wrong because configuring the router as an ABR (Area Border Router) has no effect on DR/BDR election; ABR status is about routing between areas, not about interface election roles.

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Matchingmedium

Drag and drop each OSPF LSA type on the left to its matching description on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Describes the router's own directly connected links and neighbors

Generated by the Designated Router to describe all routers attached to a multi-access segment

Advertises networks from one area into another area (inter-area routes)

Advertises the location of an Autonomous System Boundary Router (ASBR)

Advertises routes redistributed from another routing domain (external routes)

Why these pairings

LSA Type 1 (Router LSA) describes a router's own links; Type 2 (Network LSA) is generated by the DR; Type 3 (Summary LSA) advertises inter-area routes; Type 4 (ASBR Summary LSA) advertises the location of an ASBR; Type 5 (AS External LSA) advertises external routes.

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MCQeasy

In OSPF, which LSA type is used to describe routes to networks within the same area and is generated by the router that owns the network?

A.Type 1 (Router LSA)

B.Type 2 (Network LSA)

C.Type 3 (Summary LSA)

D.Type 5 (External LSA)

AnswerA

Type 1 LSAs advertise the router's links and are the most basic LSA type.

Why this answer

Type 1 (Router LSA) is correct because each OSPF router generates a Type 1 LSA to describe its directly connected links and networks within the same area. This LSA is flooded only within the originating area and is the fundamental building block for intra-area route calculation using the SPF algorithm.

Exam trap

Cisco often tests the distinction between the router that originates the LSA (Type 1) versus the DR that generates the LSA for the network segment (Type 2), causing candidates to confuse the 'owner' of the network with the DR's role.

How to eliminate wrong answers

Option B (Type 2 Network LSA) is wrong because it is generated by the Designated Router (DR) on a broadcast or NBMA network to describe the routers attached to that segment, not by the router that owns the network. Option C (Type 3 Summary LSA) is wrong because it is generated by an Area Border Router (ABR) to advertise routes from one area to another, not for intra-area networks. Option D (Type 5 External LSA) is wrong because it is generated by an Autonomous System Boundary Router (ASBR) to advertise routes redistributed from outside the OSPF domain, not for networks within the same area.

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Drag & Drophard

Drag and drop the steps of OSPF virtual link configuration across area 0 into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

Virtual links require area 0 transit area, and must be configured on both ABRs. The steps ensure proper connectivity: identify endpoints, configure on each router, and verify.

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