OSPF practice questions

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?

Trap 1: The OSPF network type is point-to-point on one router and broadcast…

Incorrect because OSPF network type mismatch typically causes issues in the 2WAY or FULL state, not EXSTART. The EXSTART state is specifically for DBD exchange.

Trap 2: The OSPF hello and dead intervals are mismatched.

Incorrect because mismatched timers prevent the adjacency from forming at all, typically leaving the routers in the INIT state.

Trap 3: The OSPF router IDs are the same.

Incorrect because duplicate router IDs prevent adjacency formation entirely, typically resulting in a state of DOWN or INIT, not EXSTART.

A
The OSPF network type is point-to-point on one router and broadcast on the other.
Why wrong: Incorrect because OSPF network type mismatch typically causes issues in the 2WAY or FULL state, not EXSTART. The EXSTART state is specifically for DBD exchange.
B
The OSPF hello and dead intervals are mismatched.
Why wrong: Incorrect because mismatched timers prevent the adjacency from forming at all, typically leaving the routers in the INIT state.
C
One router has a lower IP MTU configured on the interface, causing the DBD packet to be dropped.
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.
D
The OSPF router IDs are the same.
Why wrong: Incorrect because duplicate router IDs prevent adjacency formation entirely, typically resulting in a state of DOWN or INIT, not EXSTART.

Question 2mediummultiple choice

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?

Trap 1: The OSPF process ID is different on the routers.

Incorrect because OSPF process ID is locally significant and does not affect route installation.

Trap 2: The external route has a higher administrative distance than the…

Incorrect because administrative distance is used when comparing routes from different sources; the OSPF external route is not being installed at all, not being compared.

Trap 3: The OSPF metric for the external route is too high.

Incorrect because OSPF does not have a maximum metric that prevents route installation; even high metrics are installed.

A
The OSPF process ID is different on the routers.
Why wrong: Incorrect because OSPF process ID is locally significant and does not affect route installation.
B
The external route has a higher administrative distance than the internal route.
Why wrong: Incorrect because administrative distance is used when comparing routes from different sources; the OSPF external route is not being installed at all, not being compared.
C
The forwarding address in the type 5 LSA is not reachable via an OSPF internal route.
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.
D
The OSPF metric for the external route is too high.
Why wrong: Incorrect because OSPF does not have a maximum metric that prevents route installation; even high metrics are installed.

Question 3mediummultiple choice

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?

Trap 1: Configure area 0 as a stub area.

Incorrect because area 0 cannot be configured as a stub area; OSPF backbone area must be capable of carrying all LSA types.

Trap 2: Configure OSPF database overflow protection.

Incorrect because database overflow protection limits the number of LSAs but does not reduce flooding or LSDB size proactively.

Trap 3: Configure the ABR as an ASBR.

Incorrect because an ASBR redistributes external routes, which increases LSDB size, not reduces it.

A
Configure area 0 as a stub area.
Why wrong: Incorrect because area 0 cannot be configured as a stub area; OSPF backbone area must be capable of carrying all LSA types.
B
Configure the ABR with an area filter-list to filter type 3 LSAs.
Correct because area filter-list can be used on an ABR to filter type 3 LSAs between areas, reducing LSDB size in area 0.
C
Configure OSPF database overflow protection.
Why wrong: Incorrect because database overflow protection limits the number of LSAs but does not reduce flooding or LSDB size proactively.
D
Configure the ABR as an ASBR.
Why wrong: Incorrect because an ASBR redistributes external routes, which increases LSDB size, not reduces it.

Question 4easymultiple choice

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?

Trap 1: The OSPF router IDs are the same.

Incorrect because duplicate router IDs would cause the adjacency to fail at a later state, not INIT.

Trap 2: The OSPF process ID is different.

Incorrect because OSPF process ID is locally significant and does not affect adjacency formation.

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

Incorrect because network type mismatch typically causes issues in the 2WAY state, not INIT.

A
The OSPF router IDs are the same.
Why wrong: Incorrect because duplicate router IDs would cause the adjacency to fail at a later state, not INIT.
B
The OSPF hello interval is mismatched between the two routers.
Correct because if the hello intervals are different, the routers will not agree on the hello timer, causing the adjacency to remain in INIT.
C
The OSPF process ID is different.
Why wrong: Incorrect because OSPF process ID is locally significant and does not affect adjacency formation.
D
The OSPF network type is point-to-point on one router and point-to-multipoint on the other.
Why wrong: Incorrect because network type mismatch typically causes issues in the 2WAY state, not INIT.

Question 5easymultiple choice

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?

Trap 1: Not-so-stubby area (NSSA)

Incorrect because NSSA allows import of external routes as type 7 LSAs, which does not meet the requirement of not learning external routes.

Trap 2: Totally stubby area

Incorrect because a totally stubby area blocks both type 3 and type 5 LSAs, which would prevent learning networks in area 0 as well.

Trap 3: Standard area

Incorrect because a standard area allows all LSA types, including type 5 external routes.

A
Stub area
Correct because a stub area blocks type 5 LSAs, preventing external routes from being learned, and uses a default route for external destinations.
B
Not-so-stubby area (NSSA)
Why wrong: Incorrect because NSSA allows import of external routes as type 7 LSAs, which does not meet the requirement of not learning external routes.
C
Totally stubby area
Why wrong: Incorrect because a totally stubby area blocks both type 3 and type 5 LSAs, which would prevent learning networks in area 0 as well.
D
Standard area
Why wrong: Incorrect because a standard area allows all LSA types, including type 5 external routes.

Question 6hardmultiple choice

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?

Trap 1: The type 5 LSA has a metric of 16777215.

Incorrect because OSPF does not have a maximum metric that prevents installation; even high metrics are installed.

Trap 2: The OSPF process ID on the ASBR is different from the other routers.

Incorrect because OSPF process ID is locally significant and does not affect LSA processing.

Trap 3: The type 5 LSA is being filtered by an outbound route filter.

Incorrect because if the LSA is in the database, it has not been filtered; filtering would prevent the LSA from being in the database.

A
The ASBR is not reachable via an OSPF internal route.
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.
B
The type 5 LSA has a metric of 16777215.
Why wrong: Incorrect because OSPF does not have a maximum metric that prevents installation; even high metrics are installed.
C
The OSPF process ID on the ASBR is different from the other routers.
Why wrong: Incorrect because OSPF process ID is locally significant and does not affect LSA processing.
D
The type 5 LSA is being filtered by an outbound route filter.
Why wrong: Incorrect because if the LSA is in the database, it has not been filtered; filtering would prevent the LSA from being in the database.

Question 7mediummultiple choice

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?

Trap 1: Configure the OSPF cost on the interface connecting to the…

Incorrect because interface cost affects internal routes, not external routes. External routes use the metric set during redistribution.

Trap 2: Use the 'max-metric' command on the router connecting to the less…

Incorrect because the 'max-metric' command is used to advertise a high cost for locally originated routes, not for external routes.

Trap 3: Configure the OSPF network type to point-to-point on both…

Incorrect because network type does not influence external route path selection.

A
Configure the OSPF cost on the interface connecting to the preferred ISP to a lower value.
Why wrong: Incorrect because interface cost affects internal routes, not external routes. External routes use the metric set during redistribution.
B
Use the 'distance ospf external' command to set a higher administrative distance for external routes from the less preferred ISP.
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.
C
Use the 'max-metric' command on the router connecting to the less preferred ISP.
Why wrong: Incorrect because the 'max-metric' command is used to advertise a high cost for locally originated routes, not for external routes.
D
Configure the OSPF network type to point-to-point on both interfaces.
Why wrong: Incorrect because network type does not influence external route path selection.

Question 8hardmultiple choice

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?

Trap 1: The OSPF router priority is set to 0 on both routers.

Incorrect because if both routers have priority 0, they cannot become DR/BDR, but they can still form full adjacency with each other if the network type is broadcast.

Trap 2: The OSPF area ID is different.

Incorrect because mismatched area IDs would prevent the adjacency from reaching 2WAY; they would be stuck in INIT.

Trap 3: The Frame Relay map is missing for the broadcast keyword.

Incorrect because missing broadcast keyword would prevent hello packets from being sent, causing the adjacency to be stuck in DOWN or INIT.

A
The OSPF network type is non-broadcast and the neighbors are not manually configured.
Correct because in non-broadcast networks, OSPF neighbors must be manually configured; otherwise, the adjacency will remain in 2WAY.
B
The OSPF router priority is set to 0 on both routers.
Why wrong: Incorrect because if both routers have priority 0, they cannot become DR/BDR, but they can still form full adjacency with each other if the network type is broadcast.
C
The OSPF area ID is different.
Why wrong: Incorrect because mismatched area IDs would prevent the adjacency from reaching 2WAY; they would be stuck in INIT.
D
The Frame Relay map is missing for the broadcast keyword.
Why wrong: Incorrect because missing broadcast keyword would prevent hello packets from being sent, causing the adjacency to be stuck in DOWN or INIT.

Question 9easymultiple choice

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?

Trap 1: Configure the OSPF network type as point-to-point on all interfaces.

Incorrect because point-to-point network type eliminates DR election entirely, but the question asks to prevent the router from becoming DR, not to eliminate DR election.

Trap 2: Use the 'ip ospf dr-priority' command to set a high priority on…

Incorrect because this would not prevent the local router from becoming DR; it only influences election.

Trap 3: Configure the router as an ABR.

Incorrect because being an ABR does not affect DR election.

A
Set the OSPF priority to 0 on all interfaces.
Correct because a priority of 0 means the router will not be elected as DR or BDR.
B
Configure the OSPF network type as point-to-point on all interfaces.
Why wrong: Incorrect because point-to-point network type eliminates DR election entirely, but the question asks to prevent the router from becoming DR, not to eliminate DR election.
C
Use the 'ip ospf dr-priority' command to set a high priority on other routers.
Why wrong: Incorrect because this would not prevent the local router from becoming DR; it only influences election.
D
Configure the router as an ABR.
Why wrong: Incorrect because being an ABR does not affect DR election.

Question 10mediummultiple choice

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?

Trap 1: R1 is the Backup Designated Router (BDR) on this segment.

The state field does not show BDR; R1's own state is not displayed, but the neighbor states indicate R1 is a DROTHER.

Trap 2: R1 has a full OSPF adjacency with the neighbor 10.0.0.3.

The state for 10.0.0.3 is 2WAY, not FULL, so only a two-way relationship exists.

Trap 3: The OSPF network type is point-to-point.

The presence of DR/BDR states indicates a broadcast or NBMA network type, not point-to-point.

A
R1 is the Backup Designated Router (BDR) on this segment.
Why wrong: The state field does not show BDR; R1's own state is not displayed, but the neighbor states indicate R1 is a DROTHER.
B
R1 has a full OSPF adjacency with the neighbor 10.0.0.3.
Why wrong: The state for 10.0.0.3 is 2WAY, not FULL, so only a two-way relationship exists.
C
R1 is a DROTHER on this segment.
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.
D
The OSPF network type is point-to-point.
Why wrong: The presence of DR/BDR states indicates a broadcast or NBMA network type, not point-to-point.

Question 11hardmultiple choice

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?

Trap 1: R2 is the Backup Designated Router on this segment.

The state is DR, not BDR.

Trap 2: The OSPF cost to reach the network 192.168.1.0/24 is 20.

The cost on this interface is 10, not 20.

Trap 3: R2 will send hello packets every 40 seconds.

The hello interval is 10 seconds, not 40.

A
R2 has a full OSPF adjacency with all neighbors on this segment.
The adjacent neighbor count is 2, equal to the neighbor count, meaning all neighbors are fully adjacent.
B
R2 is the Backup Designated Router on this segment.
Why wrong: The state is DR, not BDR.
C
The OSPF cost to reach the network 192.168.1.0/24 is 20.
Why wrong: The cost on this interface is 10, not 20.
D
R2 will send hello packets every 40 seconds.
Why wrong: The hello interval is 10 seconds, not 40.

Question 12mediummultiple choice

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?

Trap 1: The route to 10.1.1.0/24 is in the same OSPF area as R3.

IA means inter-area, so it is from a different area.

Trap 2: The metric for 10.3.3.0/24 includes the internal cost to the ASBR.

E2 routes do not include internal cost; the metric shown is the external cost only.

Trap 3: R3 is an ASBR.

There is no indication that R3 is redistributing routes; it is receiving external routes.

A
The route to 10.3.3.0/24 is an external route redistributed into OSPF.
O E2 indicates an OSPF external route of type 2, typically redistributed from another routing protocol.
B
The route to 10.1.1.0/24 is in the same OSPF area as R3.
Why wrong: IA means inter-area, so it is from a different area.
C
The metric for 10.3.3.0/24 includes the internal cost to the ASBR.
Why wrong: E2 routes do not include internal cost; the metric shown is the external cost only.
D
R3 is an ASBR.
Why wrong: There is no indication that R3 is redistributing routes; it is receiving external routes.

Question 13hardmultiple choice

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?

Trap 1: Router 1.1.1.1 has three OSPF-enabled interfaces.

The link count for 1.1.1.1 is 2, not 3.

Trap 2: Router 4.4.4.4 is the BDR on the segment.

The BDR is not indicated in the database; the Net Link State is only from the DR.

Trap 3: There are multiple broadcast segments in area 0.

Only one Net Link State is listed, suggesting one broadcast segment.

A
Router 2.2.2.2 is the Designated Router on the segment 192.168.1.0/24.
The Net Link State is originated by the DR, and the ADV Router is 2.2.2.2, so it is the DR.
B
Router 1.1.1.1 has three OSPF-enabled interfaces.
Why wrong: The link count for 1.1.1.1 is 2, not 3.
C
Router 4.4.4.4 is the BDR on the segment.
Why wrong: The BDR is not indicated in the database; the Net Link State is only from the DR.
D
There are multiple broadcast segments in area 0.
Why wrong: Only one Net Link State is listed, suggesting one broadcast segment.

Question 14mediummultiple choice

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?

Trap 1: Router 2.2.2.2 is an Area Border Router.

It is labeled ASBR, not ABR.

Trap 2: Router 1.1.1.1 is redistributing external routes into OSPF.

ASBR does that; ABR connects areas.

Trap 3: The route to 2.2.2.2 is an inter-area route.

It is marked 'i' for intra-area.

A
Router 1.1.1.1 connects area 0 to another OSPF area.
ABR indicates it connects multiple areas.
B
Router 2.2.2.2 is an Area Border Router.
Why wrong: It is labeled ASBR, not ABR.
C
Router 1.1.1.1 is redistributing external routes into OSPF.
Why wrong: ASBR does that; ABR connects areas.
D
The route to 2.2.2.2 is an inter-area route.
Why wrong: It is marked 'i' for intra-area.

Question 15hardmultiple choice

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?

Trap 1: R6 has formed a full adjacency with neighbor 1.1.1.1.

The state is 2WAY, not FULL.

Trap 2: The hello packet was sent to the DR/BDR multicast address 224.0.0.6.

The destination is 224.0.0.5, which is AllSPFRouters, not AllDRouters.

Trap 3: The OSPF network type is point-to-point.

Point-to-point networks skip the 2WAY state and go directly to FULL.

A
R6 has formed a full adjacency with neighbor 1.1.1.1.
Why wrong: The state is 2WAY, not FULL.
B
The hello packet was sent to the DR/BDR multicast address 224.0.0.6.
Why wrong: The destination is 224.0.0.5, which is AllSPFRouters, not AllDRouters.
C
R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.
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).
D
The OSPF network type is point-to-point.
Why wrong: Point-to-point networks skip the 2WAY state and go directly to FULL.

Question 16hardmultiple choice

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?

Trap 1: The virtual link is used to connect area 0 to a non-backbone area.

Virtual links are used to connect a non-backbone area to area 0 through another non-backbone area, not to connect area 0 directly.

Trap 2: The virtual link is down.

The output says 'is up' and 'Adjacency State FULL'.

Trap 3: The virtual link uses area 0 as the transit area.

The transit area is area 1, not area 0.

A
The virtual link is used to connect area 0 to a non-backbone area.
Why wrong: Virtual links are used to connect a non-backbone area to area 0 through another non-backbone area, not to connect area 0 directly.
B
Router 2.2.2.2 is the other endpoint of the virtual link.
The virtual link is to router 2.2.2.2, so that is the remote endpoint.
C
The virtual link is down.
Why wrong: The output says 'is up' and 'Adjacency State FULL'.
D
The virtual link uses area 0 as the transit area.
Why wrong: The transit area is area 1, not area 0.

Question 17mediummultiple choice

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?

Trap 1: Router 1.1.1.1 is the Designated Router on this segment.

The DR is 192.168.1.2, not 1.1.1.1.

Trap 2: The neighbor state is 2WAY.

The state is FULL.

Trap 3: The dead timer is 40 seconds.

The dead timer due is 34 seconds, but the configured dead interval is typically 40 seconds; however, the question asks what can be concluded from the output, and the neighbor is BDR.

A
Router 1.1.1.1 is the Designated Router on this segment.
Why wrong: The DR is 192.168.1.2, not 1.1.1.1.
B
Router 1.1.1.1 is the Backup Designated Router.
The BDR is 192.168.1.1, which is the interface address of neighbor 1.1.1.1.
C
The neighbor state is 2WAY.
Why wrong: The state is FULL.
D
The dead timer is 40 seconds.
Why wrong: The dead timer due is 34 seconds, but the configured dead interval is typically 40 seconds; however, the question asks what can be concluded from the output, and the neighbor is BDR.

Question 18mediummultiple choice

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?

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

Gi0/1 is in BDR state, not DR.

Trap 2: The loopback interface Lo0 is advertised as a /24 network.

The IP address is 9.9.9.9/32, so it is a /32.

Trap 3: R9 is an Area Border Router.

Having interfaces in area 0 and area 1 makes it an ABR, but the output does not explicitly state that; however, the question asks what can be concluded from the output, and the neighbor counts are correct.

A
R9 is the Designated Router on the segment connected to Gi0/1.
Why wrong: Gi0/1 is in BDR state, not DR.
B
R9 has two fully adjacent neighbors on Gi0/0.
The Nbrs F/C column shows 2/2, meaning 2 neighbors and 2 full adjacencies.
C
The loopback interface Lo0 is advertised as a /24 network.
Why wrong: The IP address is 9.9.9.9/32, so it is a /32.
D
R9 is an Area Border Router.
Why wrong: Having interfaces in area 0 and area 1 makes it an ABR, but the output does not explicitly state that; however, the question asks what can be concluded from the output, and the neighbor counts are correct.

Question 19mediummultiple choice

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?

Trap 1: It disables OSPF on the interface.

This command does not disable OSPF; it changes the network type.

Trap 2: It enables OSPF authentication on the interface.

Authentication is configured separately with 'ip ospf authentication-key' or 'ip ospf message-digest-key'.

Trap 3: It sets the OSPF cost to 1.

Cost is set with 'ip ospf cost' or derived from bandwidth; this command does not set cost.

A
It disables OSPF on the interface.
Why wrong: This command does not disable OSPF; it changes the network type.
B
It changes the OSPF network type to point-to-point, eliminating DR/BDR election and reducing hello timer to 10 seconds.
Point-to-point network type removes DR/BDR election and uses 10-second hello and 40-second dead timers.
C
It enables OSPF authentication on the interface.
Why wrong: Authentication is configured separately with 'ip ospf authentication-key' or 'ip ospf message-digest-key'.
D
It sets the OSPF cost to 1.
Why wrong: Cost is set with 'ip ospf cost' or derived from bandwidth; this command does not set cost.

Question 20mediummultiple choice

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?

Trap 1: The OSPF dead interval remains at the default of 40 seconds.

The dead interval is automatically adjusted to 4 times the hello interval unless explicitly set.

Trap 2: This configuration will cause OSPF to use MD5 authentication.

No authentication is configured; hello-interval does not affect authentication.

Trap 3: The OSPF network type changes to point-to-point.

The network type is not changed; it remains broadcast by default on Ethernet.

A
The OSPF dead interval is automatically set to 20 seconds.
By default, the dead interval is 4 times the hello interval, so with hello 5, dead becomes 20 seconds.
B
The OSPF dead interval remains at the default of 40 seconds.
Why wrong: The dead interval is automatically adjusted to 4 times the hello interval unless explicitly set.
C
This configuration will cause OSPF to use MD5 authentication.
Why wrong: No authentication is configured; hello-interval does not affect authentication.
D
The OSPF network type changes to point-to-point.
Why wrong: The network type is not changed; it remains broadcast by default on Ethernet.