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Read each scenario carefully and choose your answer before revealing the explanation. Then check why your choice was right or wrong. Repeat until the reasoning feels automatic.

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300-410 · topic practice

OSPF Troubleshooting (v2/v3) practice questions

Practise 300-410 Cisco CCNP ENARSI 300-410 OSPF questions covering neighbour states, router IDs, areas, timers, passive interfaces, OSPF cost, route selection, and command-output troubleshooting.

Courseiva uses original exam-style practice questions designed for learning and revision. The goal is to understand the concepts, recognise exam patterns, and improve through explanations — not memorise copied exam dumps.

Reviewed byJohnson Ajibi· MSc IT Security

20 questionsDomain: OSPF Troubleshooting (v2/v3)

Practice 10 questions Browse domain →

What the exam tests

What to know about OSPF Troubleshooting (v2/v3)

OSPF questions usually test neighbour formation, areas, router IDs, route preference, metrics and command-output interpretation.

How OSPF neighbours form and why adjacency can fail.

How router ID, area ID, timers, passive interfaces and authentication affect OSPF.

How OSPF cost influences route selection.

How to read show ip route and show ip ospf neighbor output.

Why learners struggle

Why OSPF Troubleshooting (v2/v3) questions are commonly missed

OSPF questions are often missed because learners confuse neighbour states, route selection rules, router IDs, areas, timers, and cost calculations. A question may look like it is testing OSPF, but the real decision may depend on administrative distance, route specificity, passive interfaces, DR/BDR behaviour, or command-output interpretation.

·OSPF cost vs administrative distance — they measure different things and compare differently
·2-Way vs FULL neighbour state — 2-Way is not always a failed adjacency
·DR vs BDR vs DROTHER — election depends on network type and interface priority
·Area mismatch vs timer mismatch — both prevent adjacency but for different reasons
·Passive interface vs failed adjacency — passive interfaces intentionally suppress hello packets
·Router ID selection — highest loopback address wins unless manually configured
·show ip route OSPF codes — O, O IA, O E1, O E2 describe different route sources
·OSPF external route types — E1 accumulates cost, E2 preserves the external cost only

Watch out for

Common OSPF Troubleshooting (v2/v3) exam traps

▸A matching network statement does not guarantee adjacency.
▸OSPF cost and administrative distance solve different problems.
▸Router ID may come from a loopback or manual configuration.
▸A route can exist in OSPF but still not become the installed route.

Practice set

OSPF Troubleshooting (v2/v3) questions

20 questions · select your answer, then reveal the explanation

Question 1mediummultiple choice

Review the full OSPF breakdown →

A network engineer is troubleshooting an OSPFv2 adjacency issue between two directly connected routers, R1 and R2, both running IOS-XE. The link is a point-to-point Ethernet link. The engineer issues 'show ip ospf neighbor' on R1 and sees no neighbors. 'show ip ospf interface GigabitEthernet0/0' on R1 shows 'Network Type BROADCAST', but the link is actually a point-to-point link. Both routers have 'ip ospf 1 area 0' configured on the interface. What is the most likely cause of the adjacency not forming?

Trap 1: The OSPF network type mismatch between the two routers (one is…

Both show BROADCAST, so no mismatch.

Trap 2: The interface is configured with 'ip ospf passive-interface'.

Passive interface would still allow the router to receive hellos but not send them, but the neighbor list would show the neighbor in INIT state, not absent.

Trap 3: The OSPF process is not enabled globally; 'router ospf 1' is…

If 'ip ospf 1 area 0' is configured on the interface, the process is automatically created if not already present.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The OSPF network type mismatch between the two routers (one is BROADCAST, the other is POINT-TO-POINT).
Why wrong: Both show BROADCAST, so no mismatch.
B
The routers have duplicate OSPF router IDs.
Duplicate router IDs prevent OSPF adjacency from forming; each router must have a unique router ID.
C
The interface is configured with 'ip ospf passive-interface'.
Why wrong: Passive interface would still allow the router to receive hellos but not send them, but the neighbor list would show the neighbor in INIT state, not absent.
D
The OSPF process is not enabled globally; 'router ospf 1' is missing.
Why wrong: If 'ip ospf 1 area 0' is configured on the interface, the process is automatically created if not already present.

Full breakdown with real-world context →

Question 2hardmultiple choice

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A network engineer is troubleshooting OSPFv3 on a dual-stack network. Routers R1 and R2 are connected via a serial link. Both routers have OSPFv3 configured for IPv6. The engineer runs 'show ipv6 ospf neighbor' on R1 and sees R2 as FULL/DR. However, R1 cannot ping the IPv6 address of R2's loopback interface. 'show ipv6 route ospf' on R1 does not show any OSPF routes. What is the most likely cause?

Trap 1: The OSPFv3 process has 'no ipv6 unicast-routing' enabled globally.

IPv6 unicast routing is required for OSPFv3 to function, but if it were disabled, the router would not even form adjacencies.

Trap 2: The interface on R2 is configured as passive under OSPFv3.

A passive interface would still allow the router to form adjacency with R1, but it would not advertise the prefix of that interface, yet the loopback is not on that interface.

Trap 3: The OSPFv3 process is configured with 'default-information…

This would affect only default route propagation, not the installation of OSPF routes.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The OSPFv3 process has 'no ipv6 unicast-routing' enabled globally.
Why wrong: IPv6 unicast routing is required for OSPFv3 to function, but if it were disabled, the router would not even form adjacencies.
B
The interface on R2 is configured as passive under OSPFv3.
Why wrong: A passive interface would still allow the router to form adjacency with R1, but it would not advertise the prefix of that interface, yet the loopback is not on that interface.
C
The interface on R1 does not have an IPv6 address configured.
OSPFv3 requires an IPv6 address on the interface to advertise the connected prefix; without it, the router cannot originate a route for that link, and other routes may not be learned if the neighbor also lacks IPv6 addressing.
D
The OSPFv3 process is configured with 'default-information originate always' but no default route exists.
Why wrong: This would affect only default route propagation, not the installation of OSPF routes.

Full breakdown with real-world context →

Question 3mediummultiple choice

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A network engineer is troubleshooting OSPFv2 route redistribution. R1 is an ASBR redistributing static routes into OSPF. R2, an internal router, receives the redistributed routes but they appear as O E2 routes. However, R1 also has a directly connected network 10.1.1.0/24 that is not being advertised as an OSPF route. 'show ip ospf database external' on R2 shows the redistributed static routes but not the connected network. What is the most likely cause?

Trap 1: The connected network is not included in the redistribution because…

The 'subnets' keyword affects how classful networks are redistributed, but the connected network is not a static route, so it would not be redistributed by 'redistribute static' at all.

Trap 2: The connected network is not being advertised because it is not…

That would make the connected network an internal OSPF route, not a redistributed route, but the question is about redistribution; however, the symptom is that the connected network is not in the OSPF database at all, so either method would work, but the most likely cause is that the ASBR is not redistributing connected routes.

Trap 3: The connected network is a loopback interface, and OSPF does not…

OSPF can advertise loopback interfaces if they are part of the OSPF process via network statements or redistribution.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The connected network is not included in the redistribution because the engineer used 'redistribute static' without the 'subnets' keyword.
Why wrong: The 'subnets' keyword affects how classful networks are redistributed, but the connected network is not a static route, so it would not be redistributed by 'redistribute static' at all.
B
The connected network is not being advertised because it is not part of the OSPF process; the engineer must configure 'network 10.1.1.0 0.0.0.255 area 0' under router ospf.
Why wrong: That would make the connected network an internal OSPF route, not a redistributed route, but the question is about redistribution; however, the symptom is that the connected network is not in the OSPF database at all, so either method would work, but the most likely cause is that the ASBR is not redistributing connected routes.
C
The ASBR is missing the 'redistribute connected' command under the OSPF process.
Without 'redistribute connected', the directly connected network is not advertised into OSPF, even if the interface is enabled for OSPF (which it may not be).
D
The connected network is a loopback interface, and OSPF does not advertise loopback networks by default.
Why wrong: OSPF can advertise loopback interfaces if they are part of the OSPF process via network statements or redistribution.

Full breakdown with real-world context →

Question 4hardmultiple choice

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A network engineer is troubleshooting an OSPFv2 adjacency issue between two routers across a Frame Relay network. R1 and R2 are connected via a point-to-point subinterface. The engineer configures 'ip ospf network point-to-point' on both subinterfaces. However, the adjacency does not form. 'show ip ospf interface' on R1 shows the interface is up and OSPF is enabled, but no neighbors are seen. What is the most likely cause?

Trap 1: The OSPF network type is set to broadcast, causing a DR/BDR…

The engineer set it to point-to-point, so this is not the issue.

Trap 2: The subinterface is not configured with an IP address.

If there were no IP address, OSPF would not be enabled on the interface.

Trap 3: The OSPF hello and dead timers are mismatched between R1 and R2.

While timer mismatch can cause adjacency issues, it is less likely than a Layer 2 problem, and the stem does not indicate any timer configuration.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The OSPF network type is set to broadcast, causing a DR/BDR election that fails on a point-to-point subinterface.
Why wrong: The engineer set it to point-to-point, so this is not the issue.
B
The subinterface is not configured with an IP address.
Why wrong: If there were no IP address, OSPF would not be enabled on the interface.
C
The Frame Relay map is missing or the DLCI is not assigned to the subinterface.
Without a proper DLCI mapping, the router cannot send Layer 2 frames to the neighbor, preventing OSPF hello packets from being exchanged.
D
The OSPF hello and dead timers are mismatched between R1 and R2.
Why wrong: While timer mismatch can cause adjacency issues, it is less likely than a Layer 2 problem, and the stem does not indicate any timer configuration.

Full breakdown with real-world context →

Question 5hardmultiple choice

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A network engineer is troubleshooting an OSPFv3 issue where a router R1 is not learning routes from a neighbor R2. The adjacency is FULL, but 'show ipv6 route ospf' on R1 shows only a default route. R2 is an ASBR redistributing connected routes into OSPFv3. 'show ipv6 ospf database external' on R1 shows the external routes, but they are not installed in the routing table. What is the most likely cause?

Trap 1: The external routes have a metric of 16777214, which is considered…

While a metric that high could prevent installation, it is not typical for redistributed connected routes.

Trap 2: The router R1 does not have IPv6 unicast routing enabled.

If IPv6 unicast routing were disabled, OSPFv3 would not form adjacencies or install any routes.

Trap 3: The external routes are type 5 LSAs but the router is in a totally…

Totally stubby areas block type 5 LSAs entirely, so they would not appear in the database.

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A
The router R1 has a distribute-list in the OSPFv3 process that filters out the external routes.
A distribute-list can filter routes from being installed in the routing table even if they are in the LSDB.
B
The external routes have a metric of 16777214, which is considered infinite.
Why wrong: While a metric that high could prevent installation, it is not typical for redistributed connected routes.
C
The router R1 does not have IPv6 unicast routing enabled.
Why wrong: If IPv6 unicast routing were disabled, OSPFv3 would not form adjacencies or install any routes.
D
The external routes are type 5 LSAs but the router is in a totally stubby area.
Why wrong: Totally stubby areas block type 5 LSAs entirely, so they would not appear in the database.

Full breakdown with real-world context →

Question 6mediummultiple choice

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A network engineer is troubleshooting an OSPFv2 route flapping issue. The router R1 is learning a route to 192.168.1.0/24 via two different paths: one through R2 and one through R3. The route is flapping between the two paths every few seconds. 'show ip ospf interface' shows that both interfaces are stable. What is the most likely cause?

Trap 1: The route is being redistributed by both R2 and R3 with different…

Different metrics would cause the router to prefer one path, not flap.

Trap 2: The OSPF network type on the interfaces is set to broadcast,…

If the interfaces are stable, the DR/BDR election is stable.

Trap 3: The link between R1 and R2 has a high error rate causing…

The stem says the interfaces are stable, indicating no Layer 1 issues.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The routers R2 and R3 have the same OSPF router ID.
Duplicate router IDs can cause OSPF to see the same route from two different neighbors as different, leading to route flapping.
B
The route is being redistributed by both R2 and R3 with different metrics.
Why wrong: Different metrics would cause the router to prefer one path, not flap.
C
The OSPF network type on the interfaces is set to broadcast, causing DR/BDR instability.
Why wrong: If the interfaces are stable, the DR/BDR election is stable.
D
The link between R1 and R2 has a high error rate causing intermittent packet loss.
Why wrong: The stem says the interfaces are stable, indicating no Layer 1 issues.

Full breakdown with real-world context →

Question 7mediummultiple choice

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A network engineer is troubleshooting an OSPFv2 adjacency issue between two routers connected via a VLAN trunk. R1 and R2 are in different VLANs but are connected through a Layer 2 switch. The engineer has configured 'ip ospf 1 area 0' on the subinterfaces. The adjacency forms but is stuck in INIT state. What is the most likely cause?

Trap 1: The OSPF hello interval is mismatched between the two routers.

A hello interval mismatch would cause the adjacency to not form at all, not to be stuck in INIT.

Trap 2: The subinterfaces are in different VLANs, preventing Layer 2…

If they were in different VLANs, the routers would not receive each other's hellos, so no adjacency would form.

Trap 3: The OSPF network type is set to point-to-point on one side and…

A network type mismatch would cause the adjacency to be stuck in EXSTART or EXCHANGE, not INIT.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The routers have the same OSPF router ID.
When a router receives a hello packet with its own router ID, it ignores it, causing the adjacency to stay in INIT.
B
The OSPF hello interval is mismatched between the two routers.
Why wrong: A hello interval mismatch would cause the adjacency to not form at all, not to be stuck in INIT.
C
The subinterfaces are in different VLANs, preventing Layer 2 communication.
Why wrong: If they were in different VLANs, the routers would not receive each other's hellos, so no adjacency would form.
D
The OSPF network type is set to point-to-point on one side and broadcast on the other.
Why wrong: A network type mismatch would cause the adjacency to be stuck in EXSTART or EXCHANGE, not INIT.

Full breakdown with real-world context →

Question 8hardmultiple choice

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A network engineer is troubleshooting an OSPFv2 issue where a router R1 is not receiving a specific route for 10.0.0.0/8 from a neighbor R2. The adjacency is FULL, and 'show ip ospf database' on R1 shows the LSA for 10.0.0.0/8 as a type 5 LSA. However, the route is not in the routing table. 'show ip route 10.0.0.0' shows no route. What is the most likely cause?

Trap 1: The route is a type 5 LSA, but the router is in a stub area.

Stub areas block type 5 LSAs, so the LSA would not be in the database.

Trap 2: The router has a higher administrative distance for OSPF routes,…

If there were another route, it would appear in the routing table; the stem says no route is present.

Trap 3: The route has a metric of 16777214, which is considered infinite.

A metric that high would still be installed, but the router would not use it; however, the route would appear in the routing table as a candidate.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The router R1 has a distribute-list applied to the OSPF process that filters the route 10.0.0.0/8.
A distribute-list can prevent a route from being installed in the routing table even if the LSA is in the database.
B
The route is a type 5 LSA, but the router is in a stub area.
Why wrong: Stub areas block type 5 LSAs, so the LSA would not be in the database.
C
The router has a higher administrative distance for OSPF routes, causing it to prefer another routing protocol.
Why wrong: If there were another route, it would appear in the routing table; the stem says no route is present.
D
The route has a metric of 16777214, which is considered infinite.
Why wrong: A metric that high would still be installed, but the router would not use it; however, the route would appear in the routing table as a candidate.

Full breakdown with real-world context →

Question 9hardmultiple choice

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A network engineer is troubleshooting an OSPFv3 adjacency issue between two routers over an IPv6-only link. The engineer configures OSPFv3 on both routers and sees that the adjacency is stuck in EXSTART state. 'debug ipv6 ospf packet' shows that the routers are exchanging DBD packets but not progressing. What is the most likely cause?

Trap 1: The routers have different OSPFv3 router IDs.

Different router IDs are required for adjacency, so this would not cause an issue.

Trap 2: The OSPFv3 process is configured with 'ipv6 ospf 1 area 0' on the…

If the interface were not IPv6-enabled, OSPFv3 would not even start the adjacency process.

Trap 3: The link is a point-to-point link, but the OSPF network type is set…

A network type mismatch would cause the adjacency to be stuck in INIT or 2WAY, not EXSTART.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The OSPFv3 interface MTU is mismatched between the two routers.
An MTU mismatch prevents DBD packets from being exchanged properly, causing the adjacency to be stuck in EXSTART.
B
The routers have different OSPFv3 router IDs.
Why wrong: Different router IDs are required for adjacency, so this would not cause an issue.
C
The OSPFv3 process is configured with 'ipv6 ospf 1 area 0' on the interface, but the interface is not IPv6-enabled.
Why wrong: If the interface were not IPv6-enabled, OSPFv3 would not even start the adjacency process.
D
The link is a point-to-point link, but the OSPF network type is set to broadcast.
Why wrong: A network type mismatch would cause the adjacency to be stuck in INIT or 2WAY, not EXSTART.

Full breakdown with real-world context →

Question 10mediummultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.1.2         1   FULL/DROTHER    00:00:35    192.168.12.2    GigabitEthernet0/0
10.1.1.3         1   FULL/DR         00:00:32    192.168.13.3    GigabitEthernet0/1

Based on this output, which statement is correct?

Trap 1: Router R1 is the DR on the segment connected to GigabitEthernet0/0.

The neighbor state is DROTHER, meaning R1 is not the DR; the neighbor is DROTHER, so R1 might be DR or BDR, but the output only shows neighbor states, not R1's own role.

Trap 2: Router R1 is experiencing a neighbor timeout on GigabitEthernet0/1.

Dead time is 00:00:32, which is not near zero, so no timeout is imminent.

Trap 3: Router R1 is not receiving hello packets from 10.1.1.2.

The neighbor state is FULL, so hello packets are being received; otherwise the state would be DOWN or INIT.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
Router R1 is the DR on the segment connected to GigabitEthernet0/0.
Why wrong: The neighbor state is DROTHER, meaning R1 is not the DR; the neighbor is DROTHER, so R1 might be DR or BDR, but the output only shows neighbor states, not R1's own role.
B
Router R1 has a full adjacency with both neighbors and is in a stable state.
Both neighbors show FULL state, indicating complete adjacency. Dead times are decreasing normally, so adjacencies are stable.
C
Router R1 is experiencing a neighbor timeout on GigabitEthernet0/1.
Why wrong: Dead time is 00:00:32, which is not near zero, so no timeout is imminent.
D
Router R1 is not receiving hello packets from 10.1.1.2.
Why wrong: The neighbor state is FULL, so hello packets are being received; otherwise the state would be DOWN or INIT.

Full breakdown with real-world context →

Question 11hardmultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf database

OSPF Router with ID (10.1.1.1) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

10.1.1.1        10.1.1.1        120         0x80000002 0x00A1B2 3
10.1.1.2        10.1.1.2        200         0x80000001 0x00B2C3 2
10.1.1.3        10.1.1.3        150         0x80000003 0x00C3D4 4

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

192.168.12.2    10.1.1.2        180         0x80000001 0x00D4E5

Based on this output, what can be concluded?

Trap 1: Router R1 is the DR on the segment 192.168.12.0/24.

The net link state is advertised by 10.1.1.2, not by R1 (10.1.1.1).

Trap 2: Router 10.1.1.3 has the highest router ID.

Router IDs are 10.1.1.1, 10.1.1.2, and 10.1.1.3; 10.1.1.3 is the highest numerically, but this is not directly relevant to the database output.

Trap 3: There is a network LSA for every broadcast segment in area 0.

Only one net link state is present, so either there is only one broadcast segment or other segments have no DR elected.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
Router R1 is the DR on the segment 192.168.12.0/24.
Why wrong: The net link state is advertised by 10.1.1.2, not by R1 (10.1.1.1).
B
Router 10.1.1.2 is the DR on the segment 192.168.12.0/24.
The net link state with Link ID 192.168.12.2 is advertised by 10.1.1.2, meaning it is the DR on that segment.
C
Router 10.1.1.3 has the highest router ID.
Why wrong: Router IDs are 10.1.1.1, 10.1.1.2, and 10.1.1.3; 10.1.1.3 is the highest numerically, but this is not directly relevant to the database output.
D
There is a network LSA for every broadcast segment in area 0.
Why wrong: Only one net link state is present, so either there is only one broadcast segment or other segments have no DR elected.

Full breakdown with real-world context →

Question 12mediummultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf interface GigabitEthernet0/0

GigabitEthernet0/0 is up, line protocol is up Internet Address 192.168.12.1/24, Area 0 Process ID 1, Router ID 10.1.1.1, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) 10.1.1.2, Interface address 192.168.12.2 Backup Designated router (ID) 10.1.1.1, Interface address 192.168.12.1 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:03

Neighbor Count is 1, Adjacent neighbor count is 1

Adjacent with neighbor 10.1.1.2 (Designated Router) Suppress hello for 0 neighbor(s)

Based on this output, which statement is correct?

Trap 1: Router R1 is the Designated Router on this segment.

The state is BDR, not DR. The DR is 10.1.1.2.

Trap 2: Router R1 has a priority of 0, preventing it from becoming DR.

The priority is 1, which is the default and allows it to be BDR.

Trap 3: Router R1 is not receiving hello packets from the DR.

The adjacency is with the DR, so hello packets are being received.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
Router R1 is the Designated Router on this segment.
Why wrong: The state is BDR, not DR. The DR is 10.1.1.2.
B
Router R1 has a priority of 0, preventing it from becoming DR.
Why wrong: The priority is 1, which is the default and allows it to be BDR.
C
The dead timer is set to 40 seconds and is functioning correctly.
The dead interval is 40 seconds, and the hello timer is 10 seconds, which is standard. The adjacency is up, so timers are working.
D
Router R1 is not receiving hello packets from the DR.
Why wrong: The adjacency is with the DR, so hello packets are being received.

Full breakdown with real-world context →

Question 13easymultiple choice

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A network engineer runs the following command on Router R1:

R1# 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

O    10.2.2.0/24 [110/20] via 192.168.12.2, 00:12:34, GigabitEthernet0/0

O IA 10.3.3.0/24 [110/30] via 192.168.13.3, 00:10:21, GigabitEthernet0/1

Based on this output, what can be determined?

Trap 1: The route to 10.2.2.0/24 is an external OSPF route.

It is marked as O, which means intra-area, not external.

Trap 2: Router R1 has a default route configured.

The output states 'Gateway of last resort is not set', so no default route.

Trap 3: Both routes have the same administrative distance.

Both have [110/...], so administrative distance is 110, but the statement is true; however, the question asks for what can be determined, and B is more specific.

Study all OSPF Troubleshooting (v2/v3) common traps →

A
The route to 10.2.2.0/24 is an external OSPF route.
Why wrong: It is marked as O, which means intra-area, not external.
B
The route to 10.3.3.0/24 is learned from a different area.
The IA tag indicates it is an inter-area route, meaning it originates from another area.
C
Router R1 has a default route configured.
Why wrong: The output states 'Gateway of last resort is not set', so no default route.
D
Both routes have the same administrative distance.
Why wrong: Both have [110/...], so administrative distance is 110, but the statement is true; however, the question asks for what can be determined, and B is more specific.

Full breakdown with real-world context →

Question 14mediummultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf neighbor 10.1.1.2

 Neighbor 10.1.1.2, interface address 192.168.12.2

In the area 0 via interface GigabitEthernet0/0

Neighbor priority is 1, State is FULL, 6 state changes

DR is 10.1.1.2, BDR is 10.1.1.1 Options is 0x12 (L L S R) Dead timer due in 00:00:36

Neighbor is up for 00:15:42

Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0) Last retransmission scan length is 0, time is 0 msec Last retransmission scan time is 0 msec

Based on this output, what is the role of Router R1 on this segment?

Trap 1: Router R1 is the Designated Router.

The DR is listed as 10.1.1.2, not 10.1.1.1.

Trap 2: Router R1 is a DROTHER router.

The state is FULL, and BDR is specified, so R1 is not a DROTHER.

Trap 3: Router R1 has no special role on this segment.

It is the BDR, which is a specific role.

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A
Router R1 is the Designated Router.
Why wrong: The DR is listed as 10.1.1.2, not 10.1.1.1.
B
Router R1 is the Backup Designated Router.
The BDR is 10.1.1.1, which is R1's router ID.
C
Router R1 is a DROTHER router.
Why wrong: The state is FULL, and BDR is specified, so R1 is not a DROTHER.
D
Router R1 has no special role on this segment.
Why wrong: It is the BDR, which is a specific role.

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Question 15hardmultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf database router 10.1.1.2

OSPF Router with ID (10.1.1.1) (Process ID 1)

Router Link States (Area 0)

LS age: 150 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 10.1.1.2 Advertising Router: 10.1.1.2 LS Seq Number: 80000002 Checksum: 0x1234 Length: 48 Number of Links: 2

Link connected to: a Transit Network (Link ID) Designated Router address: 192.168.12.2 (Link Data) Router Interface address: 192.168.12.2 Number of TOS metrics: 0 TOS 0 Metrics: 10

Link connected to: a Stub Network (Link ID) Network/subnet number: 10.2.2.0 (Link Data) Network Mask: 255.255.255.0 Number of TOS metrics: 0 TOS 0 Metrics: 10

Based on this output, which statement is correct?

Trap 1: Router 10.1.1.2 is the DR on the transit network.

The Link ID is the DR address, which is 192.168.12.2, and the advertising router is 10.1.1.2, so it is the DR, but the statement is true; however, option A is more comprehensive.

Trap 2: Router 10.1.1.2 has a cost of 20 to reach the stub network.

The cost to the stub network is 10, as shown in TOS 0 Metrics.

Trap 3: Router 10.1.1.2 is not advertising any external routes.

The LSA is a router LSA, which does not include external routes; external routes are in AS-external LSAs.

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A
Router 10.1.1.2 is connected to a transit network and a stub network.
The LSA lists two links: one transit (to the DR) and one stub (10.2.2.0/24).
B
Router 10.1.1.2 is the DR on the transit network.
Why wrong: The Link ID is the DR address, which is 192.168.12.2, and the advertising router is 10.1.1.2, so it is the DR, but the statement is true; however, option A is more comprehensive.
C
Router 10.1.1.2 has a cost of 20 to reach the stub network.
Why wrong: The cost to the stub network is 10, as shown in TOS 0 Metrics.
D
Router 10.1.1.2 is not advertising any external routes.
Why wrong: The LSA is a router LSA, which does not include external routes; external routes are in AS-external LSAs.

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Question 16mediummultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf virtual-links

Virtual Link OSPF_VL0 to router 10.1.1.3 is up Run as demand circuit DoNotAge LSA allowed. Transit area 1, via interface GigabitEthernet0/0, 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 00:00:08 Adjacency State FULL

Based on this output, what can be concluded?

Trap 1: The virtual link is using area 0 as the transit area.

The transit area is area 1, not area 0.

Trap 2: Router R1 is not receiving hello packets on the virtual link.

The virtual link is a demand circuit, so hellos are suppressed; this is normal, not a problem.

Trap 3: The virtual link has a cost of 1.

The cost is 10, as shown.

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A
The virtual link is using area 0 as the transit area.
Why wrong: The transit area is area 1, not area 0.
B
The virtual link is functioning correctly and the adjacency is full.
The state is FULL and the link is up, indicating proper operation.
C
Router R1 is not receiving hello packets on the virtual link.
Why wrong: The virtual link is a demand circuit, so hellos are suppressed; this is normal, not a problem.
D
The virtual link has a cost of 1.
Why wrong: The cost is 10, as shown.

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Question 17hardmultiple choice

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A network engineer runs the following command on Router R1:

R1# show ip ospf neighbor detail

 Neighbor 10.1.1.4, interface address 192.168.14.4

In the area 0 via interface GigabitEthernet0/2

Neighbor priority is 1, State is 2WAY, 2 state changes

DR is 10.1.1.1, BDR is 10.1.1.4 Options is 0x12 (L L S R) Dead timer due in 00:00:38

Neighbor is up for 00:05:22

Based on this output, what is the problem?

Trap 1: Router R1 is the DR and the neighbor is the BDR, so the state is…

Even if R1 is DR and neighbor is BDR, they should still form a FULL adjacency, not 2WAY.

Trap 2: The dead timer is about to expire, causing the neighbor to go down.

Dead timer is 00:00:38, which is not near zero.

Trap 3: The neighbor has a lower priority than R1, so it remains in 2WAY.

Priority does not affect the state progression beyond 2WAY; all routers should go to FULL with DR/BDR.

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A
The neighbor is in 2WAY state, meaning the adjacency is not fully established.
2WAY state indicates that the routers have seen each other's hello packets but have not exchanged LSAs. FULL is required for complete adjacency.
B
Router R1 is the DR and the neighbor is the BDR, so the state is correct.
Why wrong: Even if R1 is DR and neighbor is BDR, they should still form a FULL adjacency, not 2WAY.
C
The dead timer is about to expire, causing the neighbor to go down.
Why wrong: Dead timer is 00:00:38, which is not near zero.
D
The neighbor has a lower priority than R1, so it remains in 2WAY.
Why wrong: Priority does not affect the state progression beyond 2WAY; all routers should go to FULL with DR/BDR.

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Question 18mediummultiple choice

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A network engineer runs the following command on Router R1:

R1# show ipv6 ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.1.2         1   FULL/BDR        00:00:35    FE80::2          GigabitEthernet0/0
10.1.1.3         1   FULL/DR         00:00:32    FE80::3          GigabitEthernet0/1

Based on this output, which statement is correct regarding OSPFv3?

Trap 1: Router R1 is the DR on the segment connected to GigabitEthernet0/0.

The neighbor is BDR, so R1 might be DR, but the output does not show R1's own state; the neighbor state is BDR, indicating the neighbor is not DR.

Trap 2: The OSPFv3 process is using IPv4 addresses as router IDs.

The neighbor IDs are shown as IPv4 addresses (10.1.1.2, 10.1.1.3), which is common in OSPFv3; router IDs are 32-bit numbers, often represented as IPv4 addresses.

Trap 3: Router R1 is not receiving hello packets from 10.1.1.3.

The state is FULL, so hello packets are being received.

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A
Router R1 is the DR on the segment connected to GigabitEthernet0/0.
Why wrong: The neighbor is BDR, so R1 might be DR, but the output does not show R1's own state; the neighbor state is BDR, indicating the neighbor is not DR.
B
Router R1 has a full adjacency with both neighbors in OSPFv3.
Both neighbors show FULL state, indicating complete adjacency in OSPFv3.
C
The OSPFv3 process is using IPv4 addresses as router IDs.
Why wrong: The neighbor IDs are shown as IPv4 addresses (10.1.1.2, 10.1.1.3), which is common in OSPFv3; router IDs are 32-bit numbers, often represented as IPv4 addresses.
D
Router R1 is not receiving hello packets from 10.1.1.3.
Why wrong: The state is FULL, so hello packets are being received.

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Question 19mediummultiple choice

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Examine the following OSPF configuration on router R1:

router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
 network 192.168.1.0 0.0.0.255 area 1

What is the effect of this configuration?

Trap 1: Only the interface with IP 10.0.0.1 will be in area 0; all other…

Incorrect. The wildcard mask 0.255.255.255 matches all addresses starting with 10.

Trap 2: The configuration is invalid because OSPF process 1 cannot have two…

Incorrect. OSPF can have multiple network statements in different areas.

Trap 3: The configuration will cause a routing loop between area 0 and area…

Incorrect. There is no loop; area 0 is the backbone, and area 1 is a regular area.

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A
All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1.
Correct. The wildcard mask 0.255.255.255 matches the first octet, and 0.0.0.255 matches the last octet.
B
Only the interface with IP 10.0.0.1 will be in area 0; all other 10.x.x.x interfaces are ignored.
Why wrong: Incorrect. The wildcard mask 0.255.255.255 matches all addresses starting with 10.
C
The configuration is invalid because OSPF process 1 cannot have two network statements in different areas.
Why wrong: Incorrect. OSPF can have multiple network statements in different areas.
D
The configuration will cause a routing loop between area 0 and area 1.
Why wrong: Incorrect. There is no loop; area 0 is the backbone, and area 1 is a regular area.

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Question 20mediummultiple choice

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Consider this OSPFv3 configuration on router R2:

ipv6 router ospf 10 router-id 2.2.2.2

area 0 authentication ipsec spi 256 md5 1234567890abcdef1234567890abcdef

interface GigabitEthernet0/0

ipv6 address 2001:db8:1::1/64 ipv6 ospf 10 area 0

What is the effect of this configuration?

Trap 1: Authentication is applied only to the GigabitEthernet0/0 interface,…

Incorrect. The area-level authentication applies to all interfaces in the area.

Trap 2: The configuration is invalid because OSPFv3 does not support IPsec…

Incorrect. OSPFv3 supports IPsec authentication.

Trap 3: The router-id is missing, so OSPFv3 will not start.

Incorrect. The router-id is configured as 2.2.2.2.

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A
OSPFv3 will use IPsec MD5 authentication for all packets in area 0, including on GigabitEthernet0/0.
Correct. The area authentication command applies to all interfaces in that area.
B
Authentication is applied only to the GigabitEthernet0/0 interface, not the entire area.
Why wrong: Incorrect. The area-level authentication applies to all interfaces in the area.
C
The configuration is invalid because OSPFv3 does not support IPsec authentication.
Why wrong: Incorrect. OSPFv3 supports IPsec authentication.
D
The router-id is missing, so OSPFv3 will not start.
Why wrong: Incorrect. The router-id is configured as 2.2.2.2.

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Exam traps to avoid

▸A matching network statement does not guarantee adjacency.
▸OSPF cost and administrative distance solve different problems.
▸Router ID may come from a loopback or manual configuration.
▸A route can exist in OSPF but still not become the installed route.

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